Sys.InvalidOperationException: Cannot serialize non finite numbers

The outline feature allows you to include posts in the book hierarchy, as well as move them within the hierarchy or to reorder an entire book.

Book outline
Your page will be a part of the selected book.
The parent page in the book. The maximum depth for a book and all child pages is 9. Some pages in the selected book may not be available as parents if selecting them would exceed this limit.
Pages at a given level are ordered first by weight and then by title.