Enchanted books can now be combined. Enchanted book bonuses are now
possible to transfer (it only adds 20% of the value on the book).
Emeralds added as a universal repair ingredient at a 0.5 multiplier
(tentative). Emerald blocks behave similarly at a 0.05 multiplier. 

Unenchanting items via the anvil is now possible by putting a normal
book in the magic slot. This will destroy the item at least 50% of the
time. It tentatively costs one level.