There is no logical explanation why you were able to create a book and after 2-3 months the book is not working anymore. Open the application and save another book and check what files there are saved and where. It seems that you probably deleted files that needed for the book to be opened.
Also, HP offers integrated recovery solutions. You can access these options when you restart your computer. You will have the possibility to press a key and the recovery process starts. If this is not happening, please check the files as I have mentioned earlier.