Can someone answer a question for me? I have posted a book, Sacred,by Dennis Lehane ISBN: 0380726297. The Club Wish List indicates that this book is on a wish list under ISBN-13: 978-0553505856. Both ISBN's are for the paperback version; why wouldn't the individual who wish listed this book be offered the book I posted?

Because the system goes strictly by ISBNs. There is a "similar to the book you have on your wish list" email that is sent to the person, but if they want a specific version for some reason (binding, size, cover art) then they may not order yours. You can always go to the other version and add a tag "paperback available under ISBN #9780553505856" to bring attention to your copy.

There's 63 copies of your version posted already.  So I'm guessing that those people really want the one they have on WL. It could be the cover, it could be large print or tradesize-pbs doesn't always put that info in it's listings.  Some people collect a specific cover series. The WL one could be a special issue with a bonus author interview or something.

Or it could just be that those people are inactive and the WL version is a rarer version that doesn't get posted very often.  So that WL is a remnant of when the book first came out and those people don't do PBS anymore. 

Or the two books didn't get linked.  When you look at a book, there will be links at the bottom to other versions of the book.  These show up as red or green, depending on if it is available or not.  But not all books link.  Our system is a machine and isn't perfect.  Different middle names will cause books to not link.  Such as Susan B. Jones vs Susan B Jones.  The email alerts have the same flaw.

Putting up a tag with the other number is a quick way to promote the other version.