I am trying to post a book that has two completely different ISBNs, one on the back cover and another on the copyright page.  The one on the back cover does not bring up a valid book here on PBS, but the one on the copyright page brings up the correct book / format / cover art / etc.  It is ok to post it with that ISBN even though that is NOT the number that appears on the back of the book?

Whitney, the ISBN must match that book you are posting.

From the help documents:

Do the Title, Author, ISBN and Book Type match your book EXACTLY?

I'd suggest posting your book without an ISBN. Then you can type in all the information about the book you have. Books with the shorter ISBN do get requested.

Another option is to post a thread in the book bazaar forum and describe your book as someone who reads that thread might be interested.

If the ISBN on the coverpage matches your version (HB/PB) you can post using that number.

Publishers will sometimes add another number to track books, such as copies sold to a specific chain store or book club.   The original ISBN is often on the copyright page for those books.

The one inside the book is always the correct one. Sometimes there are two for different bindings, so make sure you pick the right one. The one on the back of the book is usually right, but not always! 

Also if you're barcode scanning a mass market paperback, you want to scan the inside front cover for the correct barcode. They are different.

Thanks everyone.  I posted it using the number on the copyright page, and triple checked to make sure all details matched.  You guys rock!

When Whitney's book is ordered,iIs it permissable (when using Media Mail) for her to write on the PBS "invoice" that the ISBN matches the copyright page?  That way it will hopefully prevent a RWAP "wrong ISBN"...