The signatures are intact, the flyleaf and endsheet are in one piece, the hard cover is in one piece. It's just that the back flyleaf, along with the hard cover, has separated from the rest of the book and is flapping free. OK, I assume that the flyleaf/end sheet are attached to the back cover and ...

Hi, one of my hobbies is book binding. If you post a pic of the damage I can post some instructions that may help. Its hard to give accurate advice without seeing the book.