How should a publisher assign ISBNs to their ebooks?

So last week the BISG issued recommendations on how publishers should handle the assignment of ISBNs to their ebooks. This prompted an interesting discussion on the American Association of University Presses listserv about how the various UPs were approaching this issue. I was quite surprised to discover that many of our colleagues were assigning one ISBN per title, and that it was used for all platforms. The other most popular practice was assigning one per format, so PDFs have their own, as did AZW, ePub, etc.

Neither of those approaches makes much sense to me. Here’s my thinking on this. That third part of the BISG study, Usage Rights, that sort of gets to where we approach this. We assign ISBNs by platform, primarily for three reasons.

First, we’re a medium/smallish press doing about 50-70 titles a year, active backlist of about 1,200, but a good chunk of those are art books so not quite ready for ebooks. Let's say for 600 ISBNs in the backlist for any given platform. But we have a three-digit ISBN publisher prefix. You know, like Chicago, MIT and California. We have 100,000 ISBNs, so far we’ve used around 6,000. So the BISG-Bowker industrial complex isn’t really my issue.

Second, I’m taking a cue from physical books, though maybe I mean physical things. If the object in question is different, it should get its own identifier. A DVD has never been assigned the same UPC identifier as a VHS tape, and shouldn’t. Why would a file usable only on a Kindle device or app have the same identifier as one usable only on the iBook app? Paperbacks and hardcovers of the same edition have significantly more in common than those two consumer facing files. Some platforms allow borrowing, some don’t. Is that different enough? Borrowing sure is a premium of a feature.

Finally, if any of a publisher's platform agreements do not have a most favored nation clause on price, and you’d like to price a title differently for say a library platform with short term loans versus a direct-to-consumer platform, then you may be increasing your risk of running afoul of Robinson-Patman if those two files had the same ISBN but different prices. Probably. But I’m not a lawyer, and more importantly, I’m not your lawyer and that wasn’t legal advice.