Enchanted Book Extractor DataPack v0.1
by yosho27
for Minecraft 1.14 (18w43c)

This is essentially just to demonstrate how powerful Minecraft 1.14 commands are. The whole datapack is just 10 commands.

Throw an enchanted item, a book, and...
  ...a lapis lazuli to extract the last enchantment from the item into the book.
  ...a lapis block to extract all enchantments from the item into the book.

The lapis is consumed. The original item is not.