What an ISBN Is An ISBN (International Standard Book Number) is a 13-digit unique identifier assigned to a specific book edition and format. It allows bookstores, libraries, distributors, and retailers to identify and track the book in their systems. Governing standard: ISO 2108 ā International Standard Book Number Official reference: International ISBN Agency Source: International ISBN Agency ā https://www.isbn-international.org/content/what-isbnā ļæ½ Who Issues ISBNs in the United States In the United States, ISBNs are issued by: Bowker Bowker operates the official registration system called MyIdentifiers. Official registration site: https://www.myidentifiers.comā ļæ½ Source: ISBN.org (operated by Bowker) ā https://www.isbn.orgā ļæ½