A recent post here described a process using Markdown, InDesign, and some custom build scripts:
http://journal.stuffwithstuff.com/2021/07/29/640-pages-in-15-months/
In particular, it introduced some interesting workflows around scripting InDesign that I'd not heard of.
I'm guessing that the typesetting for each book is as unique the book itself! What tools have you found success with? Markdown? AsciiDoc? Microsoft Word? LaTeX? Something else entirely?