Books from bookshelf are now removed starting from upper left corner instead of bottom right corner. Previous behaviour was special and different from other containers, but on the other hand it was good way to make stack data type out of books which might be useful for some redstone contraptions.
Steps to reproduce
Insert 6 books into chiseled bookshelf
Place hopper under it
Observe order in which books are collected
Observed behaviour
Books are collected in order of slots: 0, 1, 2, 3, 4, 5
Expected behaviour
Books are collected in order of slots: 5, 4, 3, 2, 1, 0
This could be intentional as this is the same behavior as chests, hoppers, droppers, etc. have