I have always had great experiences here at PBS. This week I received a book that initially I thought was okay, that is until I started reading it. A couple of the chapters are underlined in pink ink no less. Considering the fact that I can read the book, it's not that bad, but I can't repost it obviously and I hate that I lost a credit. What would you do??

I've had this happen to me before.  I went back into my transaction archive and PMd the person and asked for my credit back.  She was really nice about it, saying that she didn't know it had underlining because a friend had given her the book to post.  So, you could give that a try.

When I find damage I didn't see upon receipt of the book, I just let it go.  I figure there will be some losses like that in the course of trading, and if I didn't catch it at first, the sender probably didn't either.

I second the advice given above.  There is nothing "official" you can do since you didn't notice the problem when you were receiving the book.  But perhaps the sender will buddy you a credit, since the book technically doesn't meet posting guidelines and it was posted anyway.