“ISBNs which refer to a generic ‘master’ record which provides information not on a tradable product in a specified format, but rather on a package of content tradable in a number of different formats will not be eligible for inclusion on the Nielsen Book database.”
Simply put, e-book formats should be treated like print formats. Hardcovers and trade paperbacks get different ISBNs, so any differing e-book formats should as well. Good thing we got those 979s.
Thanks to Publishers Weekly for the blurb. Go to The Bookseller online to read the release.