I've published 20+ books, mostly fiction, using LaTeX (specifically XeLaTeX), as there are a host of fine-tuning tools available through packages, basic setting

I've published 20+ books, mostly fiction, using LaTeX (specifically XeLaTeX), as there are a host of fine-tuning tools available through packages, basic settings that can be played with, and the built-in spacing that just looks...better. XeLaTeX also allows using pretty much any font you like, along with easy typographic control down to letterforms. I also like the ability to play with book/page/margin sizes that can be tested with a couple small changes to the source document & a recompile. I'm not sure I would recommend learning LaTeX just to do this, but if you're familiar with it, the rewards are there.