diff --git a/README.md b/README.md
index ce87dda..22bedce 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,42 @@ Features:
 - Does not depend on or include any library for unzipping; bring your own Zip library
 - Does not require loading whole file into memory
 - Does not care about older browsers
-- No documentation :(
 - No tests :(
 - No continuous scrolling mode :(
+
+## Demo
+
+Serve the files with a server, and open `reader.html`. Or visit https://johnfactotum.github.io/foliate-js/reader.html.
+
+## Overview
+
+The project is designed to be modular. It has two renderers, one for paginating reflowable books, and one for fixed layout. The `View` class defined in `view.js` is the one that strings everything together.
+
+Processors for each book format returns an object that implement the following interface:
+- `.sections`: an array of sections in the book. Each item has the following properties:
+    - `.load()`: returns a string of the URL that will be rendered. May be async.
+    - `.unload()`: returns nothing. If present, can be used to free the section.
+    - `.createDocument()`: returns a `Document` object of the section. Used for searching. May be async.
+    - `.size`: a number of the byte size of the section. Used for showing reading progress.
+    - `.linear`: a string. If it is `"no"`, the section is not part of the linear reading sequence.
+    - `.cfi`: base CFI string of the section. The part that goes before the `!` in CFIs.
+    - `.id`: an identifier for the section, used for getting TOC item (see below). Can be anything, as long as they can be used as keys for the `Map` object.
+- `.dir`: a string representing the page progression direction of the book (`"rtl"` or `"ltr"`).
+- `.toc`: an array representing the table of contents of the book. Each item has
+    - `.label`: a string label for the item
+    - `.href`: a string representing the destination of the item. Does not have to be a valid URL.
+    - `.subitems`: a array that contains TOC items
+- `.pageList`: same as the TOC, but for the Page List.
+- `.metadata`: an object representing the metadata of the book.
+- `.rendition`: an object that contains properties similar to the EPUB rendition properties. If `.layout` is `"pre-paginated"`, the book is rendered with the fixed layout renderer.
+- `.resolveHref(href)`: given an href string, returns an object representing the destination referenced by the href, which has the following properties:
+    - `.index`: the index of the referenced section in the `.section` array
+    - `.anchor(doc)`: given a `Document` object, returns the document fragment referred to by the href (can either be an `Element` or a `Range`), or `null`
+- `.resolveCFI(cfi)`: same as above, but with a CFI string instead of href
+- `.isExternal(href)`: returns a boolean. If `true`, the link should be opened externally.
+
+The following methods are used for getting the correct TOC and Page List item when navigating:
+- `.splitTOCHref(href)`: given an href string (from the TOC), returns an array, the first element is the `id` of the section (see above), and the second element is the fragment identifier (can be any type; see below)
+- `.getTOCFragment(doc, id)`: given a `Document` object and a fragment identifier (the one provided by `.splitTOCHref()`; see above), returns a `Node` representing the target linked by the TOC item
+
+Almost all of the properties and methods are optional. At minimum it needs `.sections` and the `.load()` method for the sections, as otherwise there won't be anything to render.