Written Book

Written books are created after a book and quill is signed. In the inventory, written books have a purple hue (similar to enchanted items) when obtained. After it has been signed, it can not be edited again (unless you use third party programs like NBTedit). The label does not say "Written Book", but what the player titles it, unless the item is spawned in through or with an inventory editor. It will say the title on the top line of the label, and "by username" on the bottom. Username is the username of the player who wrote the book, or "Player" if signed while playing offline. The icon of the written book is slightly different from the book and quill's icon, showing the same red book, but without the quill, and appears to be enchanted. The contents of a book are an extra set of data attached to the item. This means that when a book is destroyed, its contents are lost with it (unlike maps).

When written books are obtained with or inventory editors, the label will only show "Written Book" and will be blank when opened. The book is signed and cannot be edited.

Trivia

 * It is possible to trade written books for emeralds at a 1:1 ratio. This makes a "publishing business" in Minecraft highly profitable.
 * Written books are frequently used in adventure maps as a "script" of the map, while previously the map maker could only use signs.
 * Written books can be edited with the use of an NBT tag.
 * Written books do, in fact, use a separate texture than normal Books.
 * Written books have an enchantment shine, despite not being enchanted.