The Book Binder combines all enchantments from two Enchanted Books. On compatible enchantments, it works similarly to the vanilla Anvil. It is not able to process Enchanted Books with enchantments that have levels higher than in vanilla.
Enchantments will be processed into the final Enchanted Book according to certain rules.
Identical enchantments with the same level (e.g. Efficiency I ⟷ Efficiency I) are combined to the next higher enchantment level. Enchantment levels cannot exceed vanilla ones.
Identical enchantments with different levels (e.g. Impaling II ⟷ Impaling V) are combined to the highest level of the two.
Compatible enchantments on any possible gear piece (e.g. Feather Falling ⟷ Depth Strider, for Boots) are combined.
Incompatible non-exclusive enchantments on any gear piece (e.g. Power ⟷ Protection) are combined.
Incompatible exclusive enchantments on any gear piece (e.g. Silk Touch ⟷ Fortune III for a Pickaxe, Sharpness ⟷ Smite for a Sword, etc.) are not combined. The enchantment on the Enchantment Book in the first input slot (left) remains and the enchantment on the Enchanted Book in the second input slot (right) is removed.
After processing, the final Enchanted Book will be placed in an output slot.