dust jacket

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A removable paper cover used to protect the binding of a book.
• noun A cardboard sleeve in which a phonograph record is packaged.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The detachable paper cover of a book; used to protect the binding, and to provide blurb.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a paper jacket for a book; a jacket on which promotional information is usually printed