A piece of furniture with shelves for storing books. A bookcase, or bookshelf, is a piece of, furniture almost always with horizontal shelves, used to store books. It may be fitted with glass doors. A bookcase consists of a unit including two or more shelves which may not all be used to contain books or other printed materials. Shelves may be fixed or adjustable to different positions in the case. A bookshelf normally stands on some other piece of furniture such as a desk or chest. Larger books are more likely to be kept in horizontal piles and very large books flat on wide shelves.