ISBN stands for “International Standard Book Number”. It is a unique identifier for books, ebooks, tapes, and DVD’s. The ISBN numbering system is used worldwide and publishers around the globe identify their work in this standardized format.  Each title or edition must be identified by a unique ISBN. In essence, the ISBN is similar to a license plate which guarantees that each book type product is identified uniquely. If a book is available in both hardcover and softcover (perfect binding) each must have a unique ISBN assignment to differentiate the two binding types.

To complicate the matters, there are a variety of different types of digital file formats. Amazon Kindle uses MOBI, AZW (Kindle) and KF8 (Kindle Fire.) All other ebook resellers use a standardized EPUB format. As per BISG and ISBN guidelines, authors are supposed to use a separate ISBN for each digital format they provide. In practice, most independent self-publishers assign a unique ISBN to the EPUB version of their work and use it for Amazon as well. The Amazon system automatically creates a proprietary identifier called an ASIN for each title format uploaded to its database. Sales on Amazon are primarily tracked by ASIN .

It is important to note that ebooks sold on a author’s website do not require any ISBN identification.