pretty-simple VS mdBook

You can use https://hackage.haskell.org/package/pretty-simple for that. It's pretty good and it also adds color.

Looking for a few projects that make use of it, I found accelerate, hawk, polysemy and pretty-simple, so I'll be interested to poke around in their code and see how they have things set up.

I'm responsible for a number of Java products. I try to provide high-quality Javadoc for all public library interfaces, library user's guides where appropriate, and development guides for applications. The latter two take the form of MDBook documents (https://rust-lang.github.io/mdBook/), with the document source living in the GitHub repo so that it's tied to the particular software release in a natural way.

My org has used mdBook: https://rust-lang.github.io/mdBook/ (That link is itself a rendered mdBook, so that'll give you an idea of the feature set.)

(While it's definitely a Rust "thing", if you just have a set of .md files, all you need is a "SUMMARY.md" (which contains the ToC) and a small config file; i.e., you don't have to have any Rust code to use it, and it works fine without. We document a large, mostly non-Rust codebase with it.)

If you want the lowest friction, open source, easily extensible Markdown to Web, Kindle, PDF, etc. tool, highly recommend mdBook: https://github.com/rust-lang/mdBook it’s written in Rust, but you don’t have to know any Rust to use it. And then wing is all CSS; for which there are many good (free) themes.