Core Data relationships have a "Delete Rule" which controls what happens if the source object of the relationship is deleted.
In your case, it makes sense to set the "Delete Rule" for the to-many relationships Book ->> Chapter ->> Page to "Cascade", so that, for example, deleting a book automatically deletes all related chapters, which in turn deletes all related pages. (You see why it is called "cascade"!)
The inverse (to-one) relationships Page -> Chapter -> Book should be set to "Nullify", so that, for example, deleting a chapter removes the chapter from the book.
For more information, see "Relationship Delete Rules" in the "Core Data Programming Guide".