[hak8or]

I used markdown for my documentation of a embedded liux system years back (https://brainyv2.hak8or.com/) and have been very pleased. While it's not a book, it's also not a single page document.

The rust official docs are also written in markdown and thrown at mdbook (https://rust-lang.github.io/mdBook/) to generate documentation of a similar style, but it's much more book like.

I am pretty much all in for markdown based documentation for almost everything. It does what I need and nothing more.

If I need more control over styling, that's a different story, but thankfully almost all my use cases are good enough without such control.