A book is a group of written, printed, illustrated, or blank paper made of paper, parchment, or other material, fastened together to articulate on one side, and printed in ink with text and / or images. One page in a book is a leaf, and each side of the leaf is a page. A set of pages filled with text or illustrations generated in electronic format for reading on a computer screen, smartphone or e-reader device is called an e-book or e-book.

The term "book" may also refer to the subject of a literary work, or a major part of literature (e.g., children's Literature). In Library and information science, a book is called a monograph to distinguish it from a series of periodicals, magazines or newspapers. In fiction, sometimes in other types of books (for example, Biographies), a book can be divided into several parts, also known as a Book (Book 1, book 2, book 3, etc.). Fanatical readers or book collectors or book lovers are book lovers or "Bookworms" in general.

The shop where books are sold is a bookstore or bookstore. Books are also sold in some department stores, drugstores and newspaper vendors. You can also borrow books from the library. Google estimates that by 2010, about 130 million different titles had been published. In some richer countries, printed books are giving way to electronic or e-book use, although e-book sales fell in the first half of 2015.