A book with two ISBNs

[Roee]

Hello,
In this thread: https://www.goodreads.com/topic/show/...
the OP says that the book has two ISBNs.
I've updated both of the editions, but I'm asking how do these editions should be handled.

[rivka, Former Moderator]

It is very common for a book to have the ISBNs of other editions listed on its copyright page. That does not mean that single book has multiple ISBNs.

[Roee]

Thanks, Rivka.
I'll wait for the answer on the thread there.
Any clue to what is A-Format / B-Format?

[rivka, Former Moderator]

They are different sizes of paperbacks used in the UK. (Similar but not identical to "mass-market paperback" and "trade paperback" in the US.)

[Roee]

OK, thanks