Book - published work of literature or scholarship; the term has been defined by UNESCO for statistical purposes as a "non-periodical printed publication of at least 49 pages excluding covers," but no strict definition satisfactorily covers the variety of publications so identified.
Although the form, content, and provisions for making books have varied widely during their long history, some constant characteristics may be identified. The most obvious is that a book is designed to serve as an instrument of communication-the purpose of such diverse forms as the Babylonian clay tablet, the Egyptian papyrus roll, the medieval vellum or parchment codex, the printed paper codex (most familiar in modern times), microfilm, and various other media and combinations. The second characteristic of the book is its use of writing or some other system of visual symbols (such as pictures or musical notation) to convey meaning. …