Finally had some time to play around with #mdbook. And I must say, I am impressed.
Very easy to use, very intuitive. And the documentation is really excellent (and written as a mdbook...).
https://github.com/rust-lang/mdBook
https://rust-lang.github.io/mdBook/index.html
mdbook makes it really easy to put together some markdown files and create a good looking, browsable documentation.