I have a number of Drupal sites on the go, all have books pages but, despite weighting the parent page -15 and child pages sequentially up to +15 I can't display or weight pages after 31 to whatever number.
On one of my Genealogy sites (Drupal 6) I've had to create a stand-alone index page with internal links to over 1500 pages of transcribed resources, the task was mindnumbnumbingly tedious and not easy to navigate for users. Even some of the sub-categorised book pages should have more than 45 pages so this one site has become a labyrinth rather than a helpful resource.
Another site (Drupal 7) publishes short stories in episode format towards full book format, until the series is complete (Not a Blog). But, again, the shortcomings of the Book Content precludes easy chapter/edition indexing above 30 pages.
On a bit of a tangent but still related. Yet another website has sections for Tall Tales and Local Legends. It would be great to have a Book Format to cope with more than 30 pages but it would be even better to be able to create big-ish books with a selection of how pages are displayed on the parent page.