Book

Books are items crafted from paper and leather.

Bookshelves
Three books are dropped when a bookshelf is mined without silk touch or destroyed by an explosion.

Natural generation
Books can be found in stacks of 1 to 3 inside chests in the stronghold's library.

Enchanting
Books can be made into enchanted books by enchanting them on enchantment tables.

Trading
Librarian villagers will buy 8-10 books for an emerald.