Md book is great! We created a Nim version to support content written with nimib (a framework to publish html pages with Nim code and its results) and it has been very useful! https://pietroppeter.github.io/nimibook/index.html

As people are sharing other SSG (I think material for MkDocs is the absolute best for documentation sites), let me share a relatively unknown one that I find very interesting: https://github.com/dmulholl/ark

I have as next project to try and port this ark to Nim/nimib (and ideally nimibook should be refactored to use it).