Book

Books are crafted from paper and currently serve no gameplay purpose except in crafting. Books and paper can naturally occur in chests, inside strongholds.

Though it hasn't been confirmed yet, it has been mentioned that with the new code Notch made for the maps, he will be able to, in future updates, make books that players can type in and share with other players. The same thing can apply to custom paintings.

Usage
Currently the only use for books is to make bookshelves and enchantment tables. You are not able to write anything on/in books. Notch has stated that in the future he might add other uses and allow words to be put in.

Crafting
Books are crafted from three paper sheets in a vertical column. Apparently the recepie for this has been changed, and does not use up as much materials.

History
Books were added in Alpha 1.0.11. Their only use was for the Bookshelf. As of Beta 1.9, Books are usable for Enchantments.

Buch Livre Könyv 책 Boek Książka Книга