I'm no great lover of Word - some things regarding formatting are awful - but I'm pretty confused what makes it so bad an author would dump it, unless they're doing something avant-garde with formatting.
We have 1000+ page technical documents, 10 years old with hundreds (thousands?) of revisions going back to Word 97 (or earlier) and hundreds of images and tables and what-not. And they work fine.
For writing a book, I would have thought any modern WP is just fine.