delete

Mark the book as received with a problem - Damaged by Sender and ask that they return your credit and send another credit if they want the book returned to them.

Yes, I agree with Kristen. If the book was unpostable, then it should never have been posted in the first place. Definitely say that it was RWAP (Received With A Problem). This is important so that others don't get stuck with books in unpostable condition too. Everybody makes mistakes, but this is a way for PBS to keep track of offenders and get rid of habitual problem makers. If this was simply a mistake on the sender's part, then that person should return your credit, period. I also agree with you about not fronting the return postage. Why would the sender want the book back anyway? So they can post it again? It was obviously a book they were willing to get rid of and they knew it was unpostable.

Linda

If the person refuses to return your credit, I would contact TPTB as they have admitted via PM that there is something wrong with the book.  The book should never have been sent.

From the help docs:

You are not obligated to return the problem item at your expense, but if the sender gives you an extra credit or postage to do so, of course you may. 

Definitely mark it RWAP and ask for the credit back. Make them cover the postage BEFORE you send the book back, since their honesty is not shown in the best light by the way they handled this transaction, I wouldn't trust them to send you the credits after they got the book back. If they do not make the transaction right, please copy and send all of the PM interaction with this member to the Team. They usually won't get involved with individual swaps, but they will do something about members who blantantly disregard the rules of the site and admit it.

Here is the Help Center info you can send them:

If you are contacted by a requestor about a problem transaction:

• Please be courteous:
  • The requestor MAY have clicked the wrong button, or may be mistaken about whether or not the transaction was actually a problem, but that could be because she or he is new to the site, or is not clear on the rules.
  • Everyone makes mistakes sometimes. Gentle handling of this situation will minimize unpleasantness.
  • Even if you get a rude PM, do not respond in kind.  Abusive PMs should be reported to us.
  
   
• We know that no one wants to have problems with their transactions!
  • Please do not take it too much to heart if you have a book you sent marked received with a problem.
  • If you did wrong, simply learn from this, and resolve not to repeat the error.
  • One problem transaction will not mar your account! However, a pattern of poor sending will jeopardize PBS membership. Best to learn from errors before it is too late: see specific information about the different "Problem Transaction" scenarios below.
  
   
• A requestor does NOT have to return the item in a "problem" transaction
  • if the sender wants the item back, he or she should send postage or a credit to pay for its return.