The book block is the collection of sewn or glued signatures or pages that make up a book, after they have been sewn and/or glued together, but before they have had a cover put on them. The term is used in bookbinding, when referring to a book that one is going to bind or tear down.

Book block is generally used in reference to sewn, hardcover books, as these type of books are far more likely to be rebound, but it can also, just as easily, refer to a paperback book or a blank book - it is the paper contents of any book, attached together, without the protective binding.