TYPEMILL is a simple flat file CMS to create a website like this. It transforms a bunch of text files (Markdown) into a website and generates a navigation.
TYPEMILL is under construction. Right now it provides only a very basic editor and a simple admin area for settings, plugins and themes. The author-experience will be improved step by step and output formats for e-books like mobi and epub are planned for the future.
If you are a developer, you can already create your own themes and your own plugins.