I have a book of 33 chapters. These chapters are numbered with roman numbers: Chapter I, chapter II and so on.I'm a blind user, so I can't use drag & drop reorder. In Drupal 7, weight range is -15 to 15. There is a way to modify this range? Or there is an other module similar to book module, with the same navigation style?
I was surprised to hear that the weight range numbers are limited, I expected to get a number input field (so I could enter any number value) but instead, the weight choice widget is a select options type, and for the Book module weights it really is limited to
-15–15 range, and it still is in Drupal 8!
In the meantime, there is a number of modules you can use to reorder book pages a different way.
Book helper seems to be the best to try out first.
There's also a comparison page: Comparison of Node/Entity Ordering Modules
I've proposed a Drupal 8 solution to the book weight range problem. The solution is likely very similar for Drupal 7. See Increase weight range for child pages in book outlines (Book module). Corrections and suggestions for improvement are solicited and welcome.