Why does it matter what the ISBN number is on a book??? If the books title is the same. and its in the paperback or hard cover that the person is requesting.  Maybe a dumb question but I just had to ask

                     Bertie

Because some times the ISBN indicates a different release and sometimes there is something about that specific release that the requester wants. Sometimes the system will say paperback so they seem the same, but one is trade and one is MMP. Some HC have different ISBNs for the book club edition because its a different publisher. Sometimes the re-release under a different ISBN has a different cover, like the Twilight ones that have the movie cover.  Its the one way to give the requester a way to target a specific release of a book. It isn't a perfect method (like covers can often change without the ISBN changing), but its the best they can get.

I have numerous British editions of Harry Potter books on my wishlist. I want those specific editions, not just the same title and binding. (Already have all of the U.S editions.) Other people might have similar collections they are working on. A few other books I want specific editions because they are textbook-type titles and I want the newest one.

Just some examples of why ISBNs are important.