The most important identifier your book can have is the ISBN. As the U.S. ISBN Agency, Bowker is the ONLY official source of ISBNs in the United States. ISBNs provide unique identification for books and simplify the distribution of your books throughout the global supply chain. Without an ISBN, your book will not be found in most bookstores, either online, or down the street from your house.
The top three important tools for discovery are the ISBN, Barcode and Marketing your book. The 13 digit ISBN links to essential information used in sales tracking, retail inventory systems, library catalogs, bookstores, online stores, and for new digital editions for old books.
The purpose of the ISBN is to identify one specific version of a book. If you wish to have a print (hardbound or softbound) or electronic (ePUB, PDF, or MOBI) version, or even register a new version, you will need a unique ISBN for each format. This allows retailers to help the customer understand exactly which version of a title they are purchasing.
A book can be found by its ISBN and the title data connected with it, long after the publisher has ceased to sell the book itself.
You may ask - why do I need an ISBN? An ISBN is essential for linking information which allows booksellers and readers to know: what your book is about, who the author is, and who the publisher is. Along with the barcode, it is crucial for tracking sales and inventory.