The International ISBN Agency, and their national agencies such as Bowker in the U.S., have repeatedly insisted that the correct use of the ISBN system requires each format of an ebook be identified with its own ISBN, as is the case with print books. Thus a Kindle file should have its own ISBN, the ePub its own too, a PDF yet its own, and so on. However, some indie authors who have purchased their ISBNs from Bowker in the U.S. insist they can assign a single ISBN to cover all Read More …