A book like this could have been handled fairly easily in FrameMaker, but sadly Adobe has decided to position in it to be only for large enterprise shops running Windows. They're probably (rightfully) afraid it would cannabalize InDesign sales if they made it more accessible.
For example, our book is 308,000 words and 32 chapters. By the time it's done it'll probably be ~310-325k plus index. LaTeX means I can change one line in the header and have the build completely re-typeset the book according to those parameters programmatically, and it does a _very_ good job.
Re: index - how do you generate an index with Apple Pages? And I don't mean concordance, I mean a proper index. With LaTeX it's...programmatic. We provide the metadata in the form of `\index{blah}`, it generates the index for us.
It's extremely hard to find anything that's competitive on all these fronts and which is also open source. LaTeX is pretty much it, everything else is focused only on basic formatting & presentation and hasn't even gotten to a proper typesetting algorithm.
https://programmingforresearch.wordpress.com/2012/03/23/word...
Though people have been trying to solve this in Word and templates but those still fail at technical books still IMHO.