I had a text book (pedagogy) come up on my WL.  I have been waiting for a long time for it so I was happy to see it.  Because it is a textbook, I PMd the sender and asked her to please let me know if the book was in reasonable condition without A LOT of underlining and highlighting.  I indicated that I was going to accept the book but I just wanted a general idea of what I was getting.

After a day, there was no response so I just accepted.  As of this morning, the label has been printed and I'm assuming that the book will be mailed within the next five days.

IF the book gets here and there is an absurd amount of  underlining or highlighting (obscures text etc), am I within my rights to ask for my credit back since the sender did not respond to my initial PM? (Clearly, I am going to be reasonable about underlining and highlighting!!)

This is really just a hypothetical question.  The greatest likelihood is that the book will arrive in terrific condition and there will be no issue but in the event that there is an issue and considering that I never received a response to my PM, what is my recourse?

If there is any highlighting or writing, the sender was required to PM you in the first place, before mailing.  And, get your acceptance of the book beforemailing.

If there is not writing, then they are not required to PM you about the book.

Your options are the same as any other postable / unpostable book ... RWAP it if it comes in a state unacceptable to you.

Yes, you could RWAP. You aren't even required to PM about a textbook. The sender should have done that. Maybe since they didn't (and didn't respond to your PM) it means it's without highlighting and underlining. Hopefully that's the case!

Yes, I'm expecting that this is a book that meets guidelines so there won't be a problem!