Any Explanation for this ISBN13 Situation?

[Suzanne]

A single book has two ISBN13 printed on the book.

What does this mean? The copyright page says 978-0-7710-1255-6.

The backcover of the paperback says 978-0-7710-1258-7.

All I can think is maybe it has to do something with them skipping the hardcover edition directly to the trade edition paperback for the 3rd book of the series.

https://archive.org/details/veryboldl...

The web archives stopped before this was published so I can't see how they summarized the situation (website now merged into Penguine Random House Canada).

https://web.archive.org/web/200710260...

The first two books had both a hardcover (978-0-7710-1147-4, 978-0-7710-1149-8) and a trade paperback (0-7710-1148-1, 978-0-7710-1257-0).


This gave me a lot of trouble because resellers use them interchangeably and I got so confused trying to hunt down a copy of the hardcover. Only to find out it doesn't exist. I'd thought the paperback sellers were just using the hardcover ISBN by mistake.

Thanks.