Understanding ISBNs: How the 13-Digit Book Identifier Works, Who Issues It, and Why It Matters to Advertising Platforms

An ISBN is a 13-digit identifier assigned to a particular edition and format of a book from a particular publisher. The hardcover, EPUB, and audiobook versions of the same book each have a different number. ISBNs are defined by ISO 2108 and administered through more than 150 national agencies.