What is book?

answer from Wikipedia :

 A  book   is a medium for recording   information   in the form of   writing   or   images , typically composed of many   pages   (made of   papyrus ,   parchment ,   vellum , or   paper )   bound   together and protected by a   cover . [1]   The technical term for this physical arrangement is   codex   (plural,   codices ). In the history of hand-held physical supports for extended written compositions or records, the codex replaces its predecessor, the   scroll . A single sheet in a codex is a   leaf   and each side of a leaf is a   page .