Don't send the book back unless you get your credit back first, PLUS another credit to cover the cost of postage.  PBS rules state that you are not obligated to send back a book unless you wish to.  I would go to the Help Center and copy the passage about this and paste it into your PM to this person.  Offer to send pictures of the damage, but politely tell her that you will be happy to send the book back and mark the problem transaction as resolved upon return of your credit and an additional credit for postage, per PBS rules.  If she still refuses, then I would tell her that you have no chocie but to mark the problem transaction as unresolved.

I'm happy to send her pictures of the damage, but if she wants the book back, shouldn't she send postage BEFORE I send the book back?

Yes, she should send the postage before you send the book back.  You are under no obligation to send a damaged book back. 

I won't send a damaged book back.  It is unpostable.  I do not want to go through the trouble.  What is the point since it can't be reposted and the sender didn't want it in the first place because they posted it to their bookself?

From the Help Center:  http://www.paperbackswap.com/help/help_item.php?id=344

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.