Vladimir Keleshev has an interesting post that details his book writing process. It is, in a sense, low tech in that it uses very basic tools: Pandoc, Make, and Vim. He writes in Markdown and uses Pandoc to covert that to PDF or EPUB. It’s a workflow that I’m familiar with as it’s pretty much what I used to write my two books.
Instead of Markdown, I used Groff to produce camera ready PS or PDF. That was before I switched to Emacs so all the text entry and editing was done with Vim. And, of course, the whole process was controlled with a makefile. It was a pleasant and efficient workflow but these days I’d do it all with Org mode. The Org markdown is easy to use and allows fine tuning by adding in some LaTeX. Since it produces LaTeX as the “intermediate file,” there’s no need to balance facing page bottoms by hand, a boring and labor intensive exercise that took considerable time.
The only difficulty would be the diagrams. I had a lot of them and they were all produced by the pic preprocessor. I like the pic language and found it easy to use but if I were to write another book using Org mode, I might try something like draw.io as Keleshev did but I’d probably bite the bullet and learn PGF/TikZ or MetaPost.
These days, there are a lot of ways to prepare a book for publishing but if you want to keep things simple, Keleshev’s post may help you out.