I posted a wish list book recently.  When the member accepted the book, I clicked on the "I can mail in 2 days" button.  However, I realized this was a textbook that I'd used for an education class and it contains 4 underlined words.  I PM'd the member to see if she still wants the book, and she hasn't responded.  It must be mailed by tomorrow or the order will be cancelled.  I've PM'd the member twice.  Is there anything else I can do?

Unfortunately not.  It sounds like you've followed the help docs to a "T" so now all you can do is wait. 

writing or highlighting on the text pages is NOT OKAY

• Exception: if it is a textbook or workbook, these are expected to have highlighting/writing
  • if you post a textbook/workbook, the condition must be described to the requestor in a Personal Message
  • AND the described condition MUST BE AGREED TO before the book is sent

I let the book time out.  A day or so later I heard from the requestor, and she did want the book, so I had to repost it.  Next time, I will cancel & not let it time out.  On my transaction archive, it says something like, "Sender did not respond."  I hate those red x's!!!

Next time, I would give them respond by date and say you will cancel the request if they don't respond.  I in the PM say if you don't hear from them by the mail by date, you are assuming the conditon is acceptable to them and sending the book.  If they make a complaint, you'll have the unanswered PM you sent as a record that you informed them of the description.

another idea is to always choose the furtherest out mail by date just in case.  while I normally mail within a few days, I still choose the longest date just in case something happens.

but glad it worked out!