A book is a set of written, printed, illustrated, or blank sheets, made of ink, paper, parchment, or other materials, fastened together to hinge at one side. A single sheet within a book is a leaf, and each side of a leaf is a page. A set of text-filled or illustrated pages produced in electronic format is known as an electronic book, or e-book.

Books may also refer to works of literature, or a main division of such a work. In library and information science, a book is called a monograph, to distinguish it from serial periodicals such as magazines, journals, or newspapers. The body of all written works including books is literature. In novels and sometimes other types of books (for example, biographies), a book may be divided into several large sections, also called books (Book 1, Book 2, Book 3, and so on). An avid reader of books is a bibliophile or colloquially, bookworm.

A shop where books are bought and sold is a bookshop or bookstore. Books can also be borrowed from libraries. Googlehas estimated that as of 2010, approximately 130,000,000 distinct titles had been published.[1] In some wealthier nations, printed books are giving way to the usage of electronic or e-books,[2] though sales of e-books declined in the first half of 2015.

When writing systems were created in ancient civilizations, a variety of objects, such as stone, clay, tree bark, metal sheets, might be used for writing. The study of such inscriptions forms a major part of history. The study of inscriptions is known as epigraphy. Alphabetic writingemerged in Egypt. The Ancient Egyptians would often write on papyrus, a plant grown along the Nile River. At first the words were not separated from each other (scriptura continua) and there was no punctuation. Texts were written from right to left, left to right, or even so that alternate lines read in opposite directions. The technical term for that last type of writing is 'boustrophedon', which means literally 'ox-turning' for the way a farmer drives an ox to plough his fields.