diff --git a/doc/assets/bookdata.graphml b/doc/assets/bookdata.graphml
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+ Config
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+ Book Content
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+ CLI Args
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+ book.toml
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+ SUMMARY.md
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+ markdown
+chapters
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+ template assets
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+ BookConfig
+ lang
+project_root
+book_dest
+book_src
+template_path
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+ config
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+ render(book)
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+ MDBook
+ project_root
+books
+renderer
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+ images
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+ BookMetadata
+ title
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+publisher
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+ title
+file
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+(optional)
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+ Vec<TocItem>
+ content
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+ behaviour control,
+paths, target format
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+ paths
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diff --git a/doc/assets/bookdata.png b/doc/assets/bookdata.png
new file mode 100644
index 00000000..f206399a
Binary files /dev/null and b/doc/assets/bookdata.png differ
diff --git a/doc/assets/structs-reorganized.png b/doc/assets/structs-reorganized.png
new file mode 100644
index 00000000..cd33bb9c
Binary files /dev/null and b/doc/assets/structs-reorganized.png differ
diff --git a/doc/assets/structs-reorganized.pum b/doc/assets/structs-reorganized.pum
new file mode 100644
index 00000000..6dc4de93
--- /dev/null
+++ b/doc/assets/structs-reorganized.pum
@@ -0,0 +1,129 @@
+@startuml
+
+class book::MDBook {
+ project_root : PathBuf
+
+ books : HashMap<&'a str, Book>
+
+ renderer : Box
+ livereload : Option
+ indent_spaces: i32
+ multilingual: bool
+
+ new(root)
+}
+
+class book::book.Book {
+ config : BookConfig
+ metadata : BookMetadata
+
+ chapters: Vec
+
+ new(title)
+}
+
+class book::bookconfig.BookConfig {
+ lang : Language
+
+ project_root : PathBuf
+ book_dest : PathBuf
+ book_src : PathBuf
+ template_path : PathBuf
+
+ new(root)
+}
+
+class book::chapter.Chapter {
+title
+file
+author
+description
+css_class
+index : Vec
+
+new(title, file)
+}
+
+namespace book::toc {
+
+class TocItem {
+ content : TocContent
+ sub_items: Vec
+ new(content)
+}
+
+enum TocContent {
+ Frontmatter "Chapter"
+ Mainmatter "Chapter"
+ Backmatter "Chapter"
+ Insert "Chapter"
+ Spacer
+}
+
+}
+
+namespace book::metadata {
+
+class BookMetadata {
+ title
+ subtitle
+ description
+ publisher
+ language
+ authors
+ translators
+ number_format
+ section_names
+ new(title)
+}
+
+class Author {
+ name
+ email
+ new(name)
+}
+
+class Language {
+ name
+ code
+}
+
+class Publisher {
+ name
+ url
+ logo_src
+}
+
+enum NumberFormat {
+ Arabic
+ Roman
+ Word
+}
+
+}
+
+class renderer::html_handlebars::HtmlHandlebars {
+ new()
+ render(book: MDBook)
+}
+
+class theme::Theme {
+ index
+ css
+ favicon
+ js
+ highlight_css
+ tomorrow_night_css
+ highlight_js
+ jquery
+ new(src)
+}
+
+book::book-[hidden]->book::bookconfig
+book::book-[hidden]->book::chapter
+book::book-[hidden]->book::toc
+book::book-[hidden]->book::metadata
+
+renderer::html_handlebars::HtmlHandlebars-[hidden]->theme::Theme
+
+@enduml
diff --git a/doc/assets/structs.png b/doc/assets/structs.png
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index 00000000..c250d832
Binary files /dev/null and b/doc/assets/structs.png differ
diff --git a/doc/assets/structs.pum b/doc/assets/structs.pum
new file mode 100644
index 00000000..3637ee69
--- /dev/null
+++ b/doc/assets/structs.pum
@@ -0,0 +1,142 @@
+@startuml
+
+class book::MDBook {
+ root
+ dest
+ src
+ theme_path
+ title
+ author
+ description
+ content : Vec
+ books : HashMap<&'a str, Book>
+ renderer
+ livereload
+}
+
+class book::book.Book {
+ metadata
+ frontmatter
+ mainmatter
+ backmatter
+
+ new(title)
+}
+
+class book::bookconfig.BookConfig {
+ root
+ dest
+ src
+ theme_path
+ title
+ author
+ description
+ indent_spaces
+ multilingual
+
+ new(root)
+}
+
+class book::chapter.Chapter {
+ title
+ file
+ author
+ description
+ index
+ class
+ sub_chapters
+
+ new(title, file)
+}
+
+namespace book::bookitem {
+
+enum BookItem {
+ Chapter "String, Chapter"
+ Affix "Chapter"
+ Spacer
+}
+
+class BookItems {
+ items : &'a [BookItem]
+ current_index
+ stack : Vec<"&'a [BookItem], usize">
+}
+
+class Chapter {
+ name
+ path
+ sub_items
+
+ new(name, path)
+}
+
+}
+
+namespace book::metadata {
+
+class BookMetadata {
+ title
+ subtitle
+ description
+ publisher
+ language
+ authors
+ translators
+ number_format
+ section_names
+ new(title)
+}
+
+class Author {
+ name
+ email
+ new(name)
+}
+
+class Language {
+ name
+ code
+}
+
+class Publisher {
+ name
+ url
+ logo_src
+}
+
+enum NumberFormat {
+ Arabic
+ Roman
+ Word
+}
+
+}
+
+class renderer::html_handlebars::HtmlHandlebars {
+ new()
+ render(book: MDBook)
+}
+
+class theme::Theme {
+ index
+ css
+ favicon
+ js
+ highlight_css
+ tomorrow_night_css
+ highlight_js
+ jquery
+ new(src)
+}
+
+book::book-[hidden]->book::bookconfig
+book::book-[hidden]->book::chapter
+book::book-[hidden]->book::bookitem
+book::book-[hidden]->book::metadata
+
+book::bookitem.BookItems-[hidden]->book::bookitem.BookItem
+
+renderer::html_handlebars::HtmlHandlebars-[hidden]->theme::Theme
+
+@enduml
diff --git a/doc/doc.md b/doc/doc.md
new file mode 100644
index 00000000..961f4926
--- /dev/null
+++ b/doc/doc.md
@@ -0,0 +1,94 @@
+# Doc
+
+Diagrams are with [yEd](http://www.yworks.com/products/yed)
+and [plantuml](http://plantuml.com).
+
+## Data
+
+`MDBook::new(root)` parses CLI args and `book.toml` to create:
+
+- app config settings
+- `Book` for each language
+
+Each `Book` is given their config setting with their source- and destination
+paths.
+
+The renderer can then render each book.
+
+To render the TOC, renderer gets a Vec from summary parser.
+
+The renderer walks through the Vec. It can match content kinds in an enum and
+this way knows whether to render:
+
+- front- back- or mainmatter
+- spacer elements (vertical space in TOC but no chapter output)
+- insert chapters (no TOC link, but the chapter is part of the reading sequence)
+
+
+
+### Renderer
+
+Takes a book, which knows:
+
+- metadata
+- toc with chapters
+- config for paths
+- template assets (`template_path`)
+
+For generating pages:
+
+Book metadata, `BookMetadata` (title, author, publisher, etc.). Just recognize
+those properties which can be easily anticipated.
+
+If Renderer needs more specific data, it can be supplied in `book.toml`. It's
+the Renderer's job to open that and parse it out.
+
+Chapters are represented in a `Vec`, each item has the chapter content
+as payload.
+
+If the user wants to store attributes that are not anticipated with structs,
+they can go in a hashmap with string keys, let them be accessible from the
+templates with helpers.
+
+For generating output:
+
+- template assets, `template-path`, renderer does whatever it wants with it
+- config (root, dest, etc. folders)
+
+Renderer is seleceted by CLI or default (html). Each book is passed to this
+renderer.
+
+### Config
+
+Takes data from:
+
+- CLI args
+- book.toml
+
+## Structs
+
+### Reorganized
+
+
+
+### Currently
+
+
+
+## Notes
+
+Take config paths for as many things as possible. Let the user organize their
+project folder differently, or allow `mdbook` to function in existing projects
+with already established folders.
+
+Add config path for `SUMMARY.md`. Default is good to be in `src/`, it allows
+chapter links to work when reading the file on Github.
+
+The init command should copy the assets folder by default, it is better to make
+this choice for new users.
+
+The specific assets (CSS, templates, etc.) are closely coupled with the book
+content when the user is writing it. If the templates change when mdbook
+develops, this changes the output in a way the user doesn't expect, maybe even
+breaking their book.
+