A hardcover, hard cover, or hardback (also known as hardbound, and sometimes as case-bound) book is one bound with rigid protective covers (typically of binder's board or heavy paperboard covered with buckram or other cloth, heavy paper, or occasionally leather). It has a flexible, sewn spine which allows the book to lie flat on a surface when opened. Modern hardcovers may have the pages glued onto the spine in much the same way as paperbacks. Following the ISBN sequence numbers, books of this type may be identified by the abbreviation Hbk.
Hardcover books are often printed on acid-free paper, and they are much more durable than paperbacks, which have flexible, easily damaged paper covers. Hardcover books are marginally more costly to manufacture. Hardcovers are frequently protected by artistic dust jackets, but a "jacketless" alternative has increased in popularity: these "paper-over-board" or "jacketless" hardcover bindings forgo the dust jacket in favor of printing the cover design directly onto the board binding.