A book is a set or collection of written, printed, illustrated, or blank sheets, made of paper, parchment, or other various material, usually fastened together to hinge at one side. A single sheet within a book is called a leaf, and each side of a leaf is called a page. A book produced in electronic format is known as an electronic book (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 (e.g biographies), a book may be divided into several large sections, also called books (Book 1, Book 2, Book 3, etc). A lover of books is usually referred to as a bibliophile, a bibliophilist, or a philobiblist, or, more informally, a bookworm. A store where books are bought and sold is a bookstore or bookshop. Books can also be borrowed from libraries.

Types of books
Types of books according to their contents
A common separation by content are fiction and non-fictional books. By no means are books limited to this classification, but it is a separation that can be found in most collections, libraries, and bookstores.

Fiction Many of the books published today are fictitious stories. They are in-part or completely untrue or fantasy. Historically, paper production was considered too expensive to be used for entertainment. An increase in global literacy and print technology led to the increased publication of books for the purpose of entertainment, and allegorical social commentary. Most fiction is additionally categorized by genre.

Non-fiction
In a library, a reference book is a general type of non-fiction book which provides information as opposed to telling a story, essay, commentary, or otherwise supporting a point of view. An almanac is a very general reference book, usually one-volume, with lists of data and information on many topics. An encyclopedia is a book or set of books designed to have more in-depth articles on many topics. A book listing words, their etymology, meanings, and other information is called a dictionary. A book which is a collection of maps is an atlas. A more specific reference book with tables or lists of data and information about a certain topic, often intended for professional use, is often called a handbook. Books which try to list references and abstracts in a certain broad area may be called an index, such as Engineering Index, or abstracts such as chemical abstracts and biological abstracts.

Other types
There are several other types of books which are not commonly found under this system. Albums are books for holding a group of items belonging to a particular theme, such as a set of photographs, card collections, and memorabilia. One common example is stamp albums, which are used by many hobbyists to protect and organize their collections of postage stamps. Such albums are often made using removable plastic pages held inside in a ringed binder or other similar smolder.