Enchantment Books

Almost every time I try to use a enchantment book on a tool or armor it will either say it worked but when I exit out of the anvil it undoes what I tried doing, or it will say it worked but the new enchantment will not appear. I have the required levels and a undamaged anvil. This has been happening to my friend and I about 80% of the time we try to use enchantment books.