hi!
wondering about the same issue. it’s important to decide what is important to you – each book page to be a separate entity or not?
here are my thoughts:
1) you can treat each drupal book page as a wordpress page. you can make page hierarchy like the one in drupal
2) you can make each drupal book chapter into a page, deviding it to blocks. as a result you would get less entity count and more organized structure
3) if you add pages on a daily basis and it’s a relevant part of you website, then you can make a new category “books” and a sub-cateogry for each specific book and add posts as a pages or chapters
