Book

Books are items used in enchanting.

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

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

Trading
Librarian villagers can buy a single book as part of an enchanted book trade.

Apprentice-level Librarian villagers have a $2/3$ chance to buy 4 books for an emerald $$, and always offer the trade $$.