Put the summary of the bug you're having here
What I expected to happen was that my efficiency 2 and 3 got to 5
Describe what you thought should happen here
What actually happened was it changed to efficiency i did in the first slot (efficiency 3
Describe what happened here
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. get 2 diamond picks of efficiency 2 or higher not 5
3. try to combine them
Works as Intended
It's different as you think it is.
Book with 1 + Book with 1 = Book with 2
Book with 2 + Book with 1 = Book with 2 (not 3)
...
Book with 4 + Book with 4 = Book with 5
Detailed information: http://minecraft.gamepedia.com/Enchanting