While puting a written Book (origianl) together with a Book and Quill in the craftinginventory to get a copy of the Book will show 0 ammount for the writen Book. As long as the writen Book (original) remains in the craftinginventory you can still add Book and Quill to get more copys. As soon as you close the Inventory or try to take the writen Book (original) it disappears.
Also happens if the written Book is a Copy of Original.