ISBN

ISBN is the initialism for International Standard Book Number. A unique ISBN is normally assigned by the International ISBN Agency and its network of national agencies to each published version or edition of a book, so the hardcover, paperback, and electronic versions of a particular book will each be assigned a different ISBN. If there are also different electronic versions of the book, such as an EPUB, a MOBI and a PDF version, each of those will have a different ISBN as well. Even a change in usage rights when all else about a book’s version and format remains the same means the assignment of a new ISBN, but a simple reprint of a previous version or edition of a book does not require a new ISBN. A multi-volume publication may have an ISBN for each volume and another for the set as a whole.

Publishers ordinarily obtain groups of ISBNS to assign to their publications, but independently published books may not have ISBNs at all, although they frequently do. If a printed book has an assigned ISBN, it normally appears in the bottom right corner of the back cover, usually along with the barcode which is itself a form of the ISBN that is scanned in bookstores or other shops when the book is purchased. The ISBN may also or alternatively appear inside the book on the page dedicated to publication and copyright information, and that is commonplace to find it in e-books as well. For an audiobook provided via a CD-Rom, DVD, or another physical medium, the ISBN can appear on the disk label or the packaging but often does not. ISBNs are frequently included in the metadata and product descriptions of books posted by publishers and booksellers.

Each ISBN now consists of thirteen digits beginning with ‘978’ or ‘979,’ but 10-digit ISBNs were assigned prior to 2007 and are still valid today. A 13-digit ISBN has five parts:
1. The prefix, which is either ‘978’ or ‘979’
2. The registration group indicating the country, language-sharing group of countries or territory where the book was published
3. The registrant, who is usually also the publisher of the book
4. The publication, which is the book or title itself
5. The check digit to enable the detection of common transcription errors
A 10-digit ISBN lacks the initial prefix and uses a different mathematical formula for calculating the check digit, which may appear as an ‘X’ (the Roman numeral for ‘10’).

Both kinds of ISBNs can be separated into their individual parts using hyphens or spaces, but accurate separation is often tricky because most of the parts do not use a fixed number of digits. Even the digits representing a particular publisher or other specific elements may not remain consistent in all ISBNs associated with that publisher or element. The initialism ISBN appears before the number for clarity, as in this 13-digit example for a novel – ISBN 9781533573940 – and this applies to electronic books as well, with the use of the term e-ISBN or eISBN proving confusing and best avoided. An ISBN-A, on the other hand, is an actionable ISBN for use in the DOI (or Digital Object Identifier) system.