The International Standard Book Number (ISBN) is a unique numeric commercial book identifier that is either 10 or 13 digit in length.
The International Standard Book Number (ISBN) is a 13-digit number that uniquely identifies books and book-like products published internationally. ISBNs are the global standard for identifying titles, most retailers require ISBNs to track book inventory and buying an ISBN improves the chances your book will be found. 10-digit ISBNs can be converted to 13-digit ISBNs. One of the selling leaders for ISBNs is Bowker, the official source for ISBNs in the United States.