Any books that you put in a crafting grid to create copies are deleted after the player takes the copied books. All that is left behind is the original book that was being copied and that book is dropped on the ground. This can also happen that the original book gets deleted and the copies are kept. Also, unsigned books, that have text, can't be copied. I'm unable to provide photos unfortunately at the moment. I will try to add some if I can recreate the problem.