The dust jacket (sometimes book jacket, dust wrapper or dust cover) of a book is the detachable outer cover, usually made of paper and printed with text and illustrations. This outer cover has folded flaps that hold it to the front and back book covers. Often the back panel or flaps are printed with biographical information about the author, a summary of the book from the publisher (known as a blurb), and/or critical praise from celebrities or authorities in the book's subject area. In addition to its promotional role, the dust jacket protects the book covers from damage. However, since it is itself relatively fragile, and since dust jackets have practical, aesthetic, and sometimes financial value, the jacket may in turn be wrapped in another jacket, usually transparent, especially if the book is a library volume.