When I was playing on my survival world, I decided to take my Efficiency 3, unbreaking 3 shovel and upgrade it to efficiency 4. I took a efficiency 1 book put it in the anvil with the shovel and it would not combine. I then looked it up on the Minecraft Wiki and it says that you can get up to 5 levels of efficiency. I then made the book efficiency2 and then tried to upgrade my shovel. Nothing happened And I was putting everything in the right order. 

The Bug:

Cannot upgrade items to next efficiency level with enchanted books.

STEPS to reproduce:

Enchant an item with an enchanting table.

Grab a book to upgrade it's enchantment level.

Try to combine them in a anvil.