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 .  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 .