The ISBN was invented in the 1960s, when British bookseller W. H. Smith began computerizing its distribution system. It became an ISO standard in 1970, and now the ISBN forms the backbone of the book supply chain around the world. Certainly there are plenty of books published that do not have ISBNs. Proprietary publications that are not traded, for example, don’t require ISBNs. Books that are sold in “walled garden” environments don’t require ISBNs. So why use them?