I got this book several weeks ago and marked it received because on first inspection, it appeared to be fine.  Now, that I have started reading it, I am finding a word or two here and there underlined in pen, and notes made on the inside margins.  It's irritating. 

It is irritating, and I'm sorry it happened.  I learned that lesson too, and now I take care to flip through each book in good lighting before marking it received.

You cannot do anything officially, but you could write to the sender and let them know and try requesting your credit be refunded, if that's what you want.  It may or may not work, but you can at least bring their attention to the fact that it violated PBS guidelines.  If you do write, be sure to initiate the PM from your transaction record, so the communication will be recorded with the transaction.

Good luck!

Cheers,

Catt