I know this is an easy question, but how to I mark a book that is listed as a paperback when I received a hardback.  The title and author are the same, and there's no other problem with the book...and I'm not upset about getting a hardback instead, but do I mark it received, received with a problem, just add a note that it was listed as a paperback?  Thanks.

RWAP-Wrong Book Received. If you don't care about the format, you can make it clear you don't need the credit returned, but let them know to double-check the listing against their book from now on and make sure the four key points match, Title, Author, ISBN, and Binding.

Though of course it's also possible it's wrong in the PBS system, so you may want to check on that. It doesn't excuse it being posted incorrectly, but it would be much more understandable then.

Even if it is listed wrong in the system, we are required to check that the binding is as listed when posting.  So it is RWAP wrong book.  I usually mark it as such, send a PM that I don't want my credit back, then immediately mark it resolved.  Unless the difference is not okay with you. 

Do check to make sure that the book does not get reordered by the system.