I have a question about hardbacks.  I have a book I have no desire to read and it is a wishilist book.  It is a hardback. All the pages are intact, there are no stains, and it is without a dustjacket.  However, it looks like it has a white ring from maybe someone set a coffee mug on it?  Both of the covers are pretty straight but one curves up a little (there is no crease).  Maybe both were from a hot coffee cup? Comments appreciated.  

Is it faded, or is it stained?

Fading is postable, stains are not. I've never seen a white stain, so just taking a wild leap without looking at your book ... probably faded. But you will know best what it looks like, of course.

Everything else you mentioned is OK, including the missing dustjacket (unless your requestor has a RC for dustjackets).

Being a wish list book doesn't let it get away with being in less than postable condition. It sounds to me like it might have issues that would make a receiver question its "good condition" but only the person holding the book can really determine postability. If I got a book with a ring on it, I'd likely mark it RWAP - damaged by sender. Books don't have rings on them unless they have received damage either from staining or liquid - I'd lean towards ligiud when it is white, especially if the book cover has changed form. It sounds like something I would just offer in the Book Bazaar where I can explain the issues.