Michelangelo is a hybrid Markdown-LaTeX system for creating a book - or any other document - using Markdown files that can transparently include LaTeX commands: it is a generalization of the Thesis which I created on TwoBinPack - my MSc project in Computer Engineering.
Michelangelo is both simple and effective:
-- you can write most of the document as simple Markdown content. You can also (and should) partition it into multiple Markdown files - one per chapter
-- you should be able to include any LaTeX command in your Markdown source
Therefore, Markdown is employed as a quick and expressive shortcut syntax for LaTeX - a sort of effective syntactic sugar.