diff --git a/internal/handlers/auth.go b/internal/handlers/auth.go
index 1f7bc92..0a1e464 100644
--- a/internal/handlers/auth.go
+++ b/internal/handlers/auth.go
@@ -3,6 +3,7 @@ package handlers
 import (
 	"bookhoard/internal/database"
 	"bookhoard/internal/middleware"
+	"context"
 	"fmt"
 	"net/http"
 	"path/filepath"
@@ -74,8 +75,20 @@ type UserProfile struct {
 }
 
 type UpdateProfileRequest struct {
-	FirstName string `json:"first_name,omitempty"`
-	LastName  string `json:"last_name,omitempty"`
+	Username  string `json:"username,omitempty" validate:"omitempty,min=3,max=50"`
+	Email     string `json:"email,omitempty" validate:"omitempty,email"`
+	FirstName string `json:"first_name,omitempty" validate:"omitempty,max=100"`
+	LastName  string `json:"last_name,omitempty" validate:"omitempty,max=100"`
+	Theme     string `json:"theme,omitempty" validate:"omitempty"`
+}
+
+type AdminUpdateUserRequest struct {
+	Username  string `json:"username,omitempty" validate:"omitempty,min=3,max=50"`
+	Email     string `json:"email,omitempty" validate:"omitempty,email"`
+	FirstName string `json:"first_name,omitempty" validate:"omitempty,max=100"`
+	LastName  string `json:"last_name,omitempty" validate:"omitempty,max=100"`
+	Theme     string `json:"theme,omitempty" validate:"omitempty"`
+	Role      string `json:"role,omitempty" validate:"omitempty,oneof=user admin"`
 }
 
 // Register handles POST /api/auth/register
@@ -210,6 +223,13 @@ func (h *AuthHandler) Register(c echo.Context) error {
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
 	}
 
+	if err := h.CreateDefaultCollectionsForUser(c.Request().Context(), user.ID); err != nil {
+		if c.Request().Header.Get("HX-Request") == "true" {
+			return c.HTML(http.StatusInternalServerError, `<div class="text-red-500">Failed to create default collections</div>`)
+		}
+		return c.JSON(http.StatusInternalServerError, map[string]string{"error": "failed to create default collections"})
+	}
+
 	accessToken, err := h.generateJWTWithAllClaims(
 		uuid.UUID(user.ID.Bytes).String(),
 		user.Role,
@@ -448,25 +468,133 @@ func (h *AuthHandler) GetProfile(c echo.Context) error {
 	})
 }
 
-// UpdateProfile handles PUT /api/auth/profile
+// UpdateProfile handles PUT /api/auth/profile (self-edit) and PUT /api/auth/profile/:id (admin edit)
+// Combined handler for both self-service and admin profile updates
 func (h *AuthHandler) UpdateProfile(c echo.Context) error {
-	user := MustGetAuthenticatedUser(c)
+	currentUser := MustGetAuthenticatedUser(c)
 
-	var req UpdateProfileRequest
+	// Determine target user: URL param (admin mode) or current user (self-edit)
+	targetUserID := c.Param("id")
+	var targetUserUUID pgtype.UUID
+	isAdminMode := targetUserID != ""
+
+	if isAdminMode {
+		// Admin editing another user - validate admin role
+		if currentUser.Role != "admin" {
+			return c.JSON(http.StatusForbidden, map[string]string{"error": "admin access required"})
+		}
+		parsedUUID, err := uuid.Parse(targetUserID)
+		if err != nil {
+			return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid user id"})
+		}
+		targetUserUUID = pgtype.UUID{Bytes: [16]byte(parsedUUID), Valid: true}
+	} else {
+		// Self-edit mode
+		targetUserUUID = currentUser.ID
+	}
+
+	var req AdminUpdateUserRequest
 	if err := c.Bind(&req); err != nil {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid request"})
 	}
-
-	err := h.db.UpdateUserProfile(c.Request().Context(), database.UpdateUserProfileParams{
-		ID:        user.ID,
-		FirstName: pgtype.Text{String: req.FirstName, Valid: req.FirstName != ""},
-		LastName:  pgtype.Text{String: req.LastName, Valid: req.LastName != ""},
-	})
-	if err != nil {
-		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+	if err := c.Validate(&req); err != nil {
+		return c.JSON(http.StatusBadRequest, map[string]string{"error": err.Error()})
 	}
 
-	return c.JSON(http.StatusOK, map[string]string{"message": "profile updated"})
+	// Handle role change (admin mode only)
+	if req.Role != "" && isAdminMode {
+		if req.Role != "admin" && req.Role != "user" {
+			return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid role. must be 'admin' or 'user'"})
+		}
+
+		// Check if this is the last admin (preventing demotion)
+		users, err := h.db.ListUsers(c.Request().Context())
+		if err != nil {
+			return c.JSON(http.StatusInternalServerError, map[string]string{"error": "failed to check existing users"})
+		}
+
+		adminCount := 0
+		currentTargetUserRole := ""
+		for _, user := range users {
+			if user.Role == "admin" {
+				adminCount++
+			}
+			if user.ID.Bytes == targetUserUUID.Bytes {
+				currentTargetUserRole = user.Role
+			}
+		}
+
+		// Prevent demoting the last admin
+		if currentTargetUserRole == "admin" && req.Role == "user" && adminCount == 1 {
+			return c.JSON(http.StatusBadRequest, map[string]string{"error": "cannot demote the last admin"})
+		}
+
+		// Update role
+		_, err = h.db.UpdateUserRole(c.Request().Context(), database.UpdateUserRoleParams{
+			ID:   targetUserUUID,
+			Role: req.Role,
+		})
+		if err != nil {
+			return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		}
+	}
+
+	// Update username (if provided)
+	if req.Username != "" {
+		existingUser, err := h.db.GetUserByUsername(c.Request().Context(), req.Username)
+		if err == nil && existingUser.ID.Bytes != targetUserUUID.Bytes {
+			return c.JSON(http.StatusConflict, map[string]string{"error": "username already taken"})
+		}
+
+		err = h.db.UpdateUsername(c.Request().Context(), database.UpdateUsernameParams{
+			ID:       targetUserUUID,
+			Username: req.Username,
+		})
+		if err != nil {
+			return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		}
+	}
+
+	// Update email (if provided)
+	if req.Email != "" {
+		existingUser, err := h.db.GetUserByEmail(c.Request().Context(), req.Email)
+		if err == nil && existingUser.ID.Bytes != targetUserUUID.Bytes {
+			return c.JSON(http.StatusConflict, map[string]string{"error": "email already taken"})
+		}
+
+		err = h.db.UpdateEmail(c.Request().Context(), database.UpdateEmailParams{
+			ID:    targetUserUUID,
+			Email: req.Email,
+		})
+		if err != nil {
+			return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		}
+	}
+
+	// Update first/last name (if provided)
+	if req.FirstName != "" || req.LastName != "" {
+		err := h.db.UpdateUserProfile(c.Request().Context(), database.UpdateUserProfileParams{
+			ID:        targetUserUUID,
+			FirstName: pgtype.Text{String: req.FirstName, Valid: req.FirstName != ""},
+			LastName:  pgtype.Text{String: req.LastName, Valid: req.LastName != ""},
+		})
+		if err != nil {
+			return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		}
+	}
+
+	// Update theme (if provided)
+	if req.Theme != "" {
+		err := h.db.UpdateUserTheme(c.Request().Context(), database.UpdateUserThemeParams{
+			ID:    targetUserUUID,
+			Theme: pgtype.Text{String: req.Theme, Valid: true},
+		})
+		if err != nil {
+			return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		}
+	}
+
+	return c.JSON(http.StatusOK, map[string]string{"message": "profile updated successfully"})
 }
 
 // ListUsers handles GET /api/auth/users
@@ -604,11 +732,38 @@ type UpdatePasswordRequest struct {
 	ConfirmPassword string `json:"confirm_password" validate:"required"`
 }
 
-// UpdatePassword handles PUT /api/auth/password
+// UpdatePassword handles PUT /api/auth/password (self-change) and PUT /api/auth/password/:id (admin reset)
+// Combined handler for both self-service password change and admin password reset
 func (h *AuthHandler) UpdatePassword(c echo.Context) error {
-	user := MustGetAuthenticatedUser(c)
+	currentUser := MustGetAuthenticatedUser(c)
 
-	var req UpdatePasswordRequest
+	// Determine target user: URL param (admin mode) or current user (self-change)
+	targetUserID := c.Param("id")
+	var targetUserUUID pgtype.UUID
+	isAdminMode := targetUserID != ""
+
+	if isAdminMode {
+		// Admin resetting another user's password - validate admin role
+		if currentUser.Role != "admin" {
+			return c.JSON(http.StatusForbidden, map[string]string{"error": "admin access required"})
+		}
+		parsedUUID, err := uuid.Parse(targetUserID)
+		if err != nil {
+			return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid user id"})
+		}
+		targetUserUUID = pgtype.UUID{Bytes: [16]byte(parsedUUID), Valid: true}
+	} else {
+		// Self-change mode
+		targetUserUUID = currentUser.ID
+	}
+
+	type PasswordRequest struct {
+		CurrentPassword string `json:"current_password,omitempty"`
+		NewPassword     string `json:"new_password" validate:"required,passwordcomplex"`
+		ConfirmPassword string `json:"confirm_password" validate:"required"`
+	}
+
+	var req PasswordRequest
 	if err := c.Bind(&req); err != nil {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid request"})
 	}
@@ -616,23 +771,28 @@ func (h *AuthHandler) UpdatePassword(c echo.Context) error {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": err.Error()})
 	}
 
-	// Check if new passwords match
-	if req.NewPassword != req.ConfirmPassword {
-		return c.JSON(http.StatusBadRequest, map[string]string{"error": "new passwords do not match"})
-	}
+	// Self-change mode: require current password
+	if !isAdminMode {
+		if req.CurrentPassword == "" {
+			return c.JSON(http.StatusBadRequest, map[string]string{"error": "current password required"})
+		}
 
-	// Get current user's password hash
-	passwordHash, err := h.db.GetUserPasswordHash(c.Request().Context(), user.ID)
-	if err != nil {
-		if err == pgx.ErrNoRows {
-			return c.JSON(http.StatusNotFound, map[string]string{"error": "user not found"})
+		// Get current password hash
+		passwordHash, err := h.db.GetUserPasswordHash(c.Request().Context(), targetUserUUID)
+		if err != nil {
+			return c.JSON(http.StatusInternalServerError, map[string]string{"error": "user not found"})
+		}
+
+		// Verify current password
+		err = bcrypt.CompareHashAndPassword([]byte(passwordHash), []byte(req.CurrentPassword))
+		if err != nil {
+			return c.JSON(http.StatusUnauthorized, map[string]string{"error": "current password is incorrect"})
 		}
-		return c.JSON(http.StatusInternalServerError, map[string]string{"error": "failed to get user"})
 	}
 
-	// Verify current password
-	if err := bcrypt.CompareHashAndPassword([]byte(passwordHash), []byte(req.CurrentPassword)); err != nil {
-		return c.JSON(http.StatusUnauthorized, map[string]string{"error": "current password is incorrect"})
+	// Validate new password matches confirmation
+	if req.NewPassword != req.ConfirmPassword {
+		return c.JSON(http.StatusBadRequest, map[string]string{"error": "passwords do not match"})
 	}
 
 	// Hash new password
@@ -643,7 +803,7 @@ func (h *AuthHandler) UpdatePassword(c echo.Context) error {
 
 	// Update password
 	err = h.db.UpdatePassword(c.Request().Context(), database.UpdatePasswordParams{
-		ID:           user.ID,
+		ID:           targetUserUUID,
 		PasswordHash: string(hashedPassword),
 	})
 	if err != nil {
@@ -653,18 +813,17 @@ func (h *AuthHandler) UpdatePassword(c echo.Context) error {
 	return c.JSON(http.StatusOK, map[string]string{"message": "password updated successfully"})
 }
 
-// DeleteAccount handles DELETE /api/auth/account
-// Supports self-deletion or admin deletion of other users
-func (h *AuthHandler) DeleteAccount(c echo.Context) error {
+// DeleteUser handles DELETE /api/auth/profile (self-deletion) and DELETE /api/auth/profile/:id (admin deletion)
+// Combined handler for both self-deletion and admin deletion of users
+func (h *AuthHandler) DeleteUser(c echo.Context) error {
 	currentUser := MustGetAuthenticatedUser(c)
 
-	// Get target user ID from query parameter (for admin override) or use current user
-	targetUserID := c.QueryParam("user_id")
+	// Get target user ID from URL param (admin mode) or use current user (self-deletion)
+	targetUserID := c.Param("id")
 	var targetUserUUID pgtype.UUID
 
-	// If admin override is used, validate admin and use target
 	if targetUserID != "" {
-		// Admin override mode - check if current user is admin
+		// Admin deletion mode
 		if currentUser.Role != "admin" {
 			return c.JSON(http.StatusForbidden, map[string]string{"error": "admin access required"})
 		}
@@ -674,6 +833,7 @@ func (h *AuthHandler) DeleteAccount(c echo.Context) error {
 		}
 		targetUserUUID = pgtype.UUID{Bytes: [16]byte(parsedUUID), Valid: true}
 	} else {
+		// Self-deletion mode
 		targetUserUUID = currentUser.ID
 	}
 
@@ -802,3 +962,36 @@ func (h *AuthHandler) generateJWTWithRole(userID, userRole string) (string, erro
 func (h *AuthHandler) generateJWT(userID string) (string, error) {
 	return h.generateJWTWithRole(userID, "user")
 }
+
+func (h *AuthHandler) CreateDefaultCollectionsForUser(ctx context.Context, userID pgtype.UUID) error {
+	defaultCollections := []struct {
+		Name        string
+		Description string
+		Icon        string
+		Color       string
+		QueryType   string
+		Priority    int32
+	}{
+		{"continue-reading", "Books you're currently reading (0 < progress < 1)", "📖", "#7aa2f7", "continue-reading", 1},
+		{"recently-added", "Newly added items to this library", "🆕", "#9ece6a", "recently-added", 2},
+		{"recently-read", "Books you've finished (progress >= 1)", "✅", "#e0af68", "recently-read", 3},
+		{"not-started", "Books you haven't read yet (progress = 0 or no record)", "📕", "#f7768e", "not-started", 4},
+	}
+
+	for _, col := range defaultCollections {
+		_, err := h.db.CreateSystemCollection(ctx, database.CreateSystemCollectionParams{
+			UserID:          userID,
+			Name:            col.Name,
+			Description:     pgtype.Text{String: col.Description, Valid: true},
+			Icon:            pgtype.Text{String: col.Icon, Valid: true},
+			Color:           pgtype.Text{String: col.Color, Valid: true},
+			ShowOnDashboard: pgtype.Bool{Bool: true, Valid: true},
+			QueryType:       pgtype.Text{String: col.QueryType, Valid: true},
+			Priority:        pgtype.Int4{Int32: col.Priority, Valid: true},
+		})
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
diff --git a/internal/handlers/collections.go b/internal/handlers/collections.go
index c566cd1..4075224 100644
--- a/internal/handlers/collections.go
+++ b/internal/handlers/collections.go
@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgtype"
 	"github.com/labstack/echo/v4"
 )
@@ -848,6 +849,14 @@ func (h *CollectionHandler) PreviewCollection(c echo.Context) error {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid library_id"})
 	}
 
+	_, err = h.db.GetLibrary(c.Request().Context(), pgtype.UUID{Bytes: libUUID, Valid: true})
+	if err != nil {
+		if err == pgx.ErrNoRows {
+			return c.JSON(http.StatusBadRequest, map[string]string{"error": "library not found"})
+		}
+		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
+	}
+
 	if req.Limit <= 0 || req.Limit > 100 {
 		req.Limit = 20
 	}
diff --git a/internal/handlers/dashboard.go b/internal/handlers/dashboard.go
index d11ef3d..245e417 100644
--- a/internal/handlers/dashboard.go
+++ b/internal/handlers/dashboard.go
@@ -103,6 +103,7 @@ func (h *DashboardHandler) RestoreSystemCollection(c echo.Context) error {
 
 	var req struct {
 		CollectionName string `json:"collection_name"`
+		ResetType      string `json:"reset_type"` // "full" or "keep_books"
 	}
 
 	if err := c.Bind(&req); err != nil {
@@ -113,6 +114,10 @@ func (h *DashboardHandler) RestoreSystemCollection(c echo.Context) error {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": "collection_name required"})
 	}
 
+	if req.ResetType == "" {
+		req.ResetType = "full"
+	}
+
 	validCollections := map[string]bool{
 		"continue-reading": true,
 		"recently-added":   true,
@@ -123,7 +128,11 @@ func (h *DashboardHandler) RestoreSystemCollection(c echo.Context) error {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": "Invalid system collection name"})
 	}
 
-	err := h.dashboardService.RestoreSystemCollection(c.Request().Context(), userUUID, req.CollectionName)
+	if req.ResetType != "full" && req.ResetType != "keep_books" {
+		return c.JSON(http.StatusBadRequest, map[string]string{"error": "reset_type must be 'full' or 'keep_books'"})
+	}
+
+	err := h.dashboardService.RestoreSystemCollection(c.Request().Context(), userUUID, req.CollectionName, req.ResetType)
 	if err != nil {
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": "Failed to restore system collection"})
 	}
diff --git a/internal/services/dashboard_service.go b/internal/services/dashboard_service.go
index 1f18056..ec3e6e2 100644
--- a/internal/services/dashboard_service.go
+++ b/internal/services/dashboard_service.go
@@ -4,6 +4,7 @@ import (
 	"bookhoard/internal/database"
 	"context"
 	"encoding/json"
+	"fmt"
 
 	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5/pgtype"
@@ -142,7 +143,7 @@ func (s *DashboardService) GetDashboardSections(
 ) ([]DashboardSection, error) {
 	var results []DashboardSection
 
-	systemCollections, err := s.db.GetSystemCollectionsForDashboard(ctx)
+	systemCollections, err := s.db.GetSystemCollectionsForDashboard(ctx, pgtype.UUID{Bytes: userID, Valid: true})
 	if err != nil {
 		return nil, err
 	}
@@ -371,7 +372,36 @@ func (s *DashboardService) UpsertDashboardPreferences(ctx context.Context, param
 	return s.db.UpsertDashboardPreferences(ctx, params)
 }
 
-func (s *DashboardService) RestoreSystemCollection(ctx context.Context, userID uuid.UUID, collectionName string) error {
+func (s *DashboardService) RestoreSystemCollection(ctx context.Context, userID uuid.UUID, collectionName string, resetType string) error {
+	defaultMetadata := map[string]struct {
+		Description string
+		Icon        string
+		Color       string
+		Priority    int32
+		QueryType   string
+	}{
+		"continue-reading": {"Books you're currently reading (0 < progress < 1)", "📖", "#7aa2f7", 1, "continue-reading"},
+		"recently-added":   {"Newly added items to this library", "🆕", "#9ece6a", 2, "recently-added"},
+		"recently-read":    {"Books you've finished (progress >= 1)", "✅", "#e0af68", 3, "recently-read"},
+		"not-started":      {"Books you haven't read yet (progress = 0 or no record)", "📕", "#f7768e", 4, "not-started"},
+	}
+
+	meta, exists := defaultMetadata[collectionName]
+	if !exists {
+		return fmt.Errorf("unknown collection: %s", collectionName)
+	}
+
+	if resetType == "keep_books" {
+		return s.db.ResetSystemCollectionMetadata(ctx, database.ResetSystemCollectionMetadataParams{
+			UserID:      pgtype.UUID{Bytes: userID, Valid: true},
+			Name:        collectionName,
+			Description: pgtype.Text{String: meta.Description, Valid: true},
+			Icon:        pgtype.Text{String: meta.Icon, Valid: true},
+			Color:       pgtype.Text{String: meta.Color, Valid: true},
+			Priority:    pgtype.Int4{Int32: meta.Priority, Valid: true},
+		})
+	}
+
 	err := s.db.DeleteUserSystemCollection(ctx, database.DeleteUserSystemCollectionParams{
 		UserID: pgtype.UUID{Bytes: userID, Valid: true},
 		Name:   collectionName,
@@ -380,5 +410,15 @@ func (s *DashboardService) RestoreSystemCollection(ctx context.Context, userID u
 		return err
 	}
 
-	return nil
+	_, err = s.db.CreateSystemCollection(ctx, database.CreateSystemCollectionParams{
+		UserID:          pgtype.UUID{Bytes: userID, Valid: true},
+		Name:            collectionName,
+		Description:     pgtype.Text{String: meta.Description, Valid: true},
+		Icon:            pgtype.Text{String: meta.Icon, Valid: true},
+		Color:           pgtype.Text{String: meta.Color, Valid: true},
+		ShowOnDashboard: pgtype.Bool{Bool: true, Valid: true},
+		QueryType:       pgtype.Text{String: meta.QueryType, Valid: true},
+		Priority:        pgtype.Int4{Int32: meta.Priority, Valid: true},
+	})
+	return err
 }