Today I received a book that has the cover attached by tape and the cover shows quite a bit of wear (lots of folds, bending and white lines).  Can I ask for my credit back, or is this still considered "good" condition by paperbackswap conditions?  Thank you for your assistance and advice! 

The folds don't necessarily make it unpostable, it could be argued that they make the book "excessively worn", but that is where the condition guidelines get a bit subjective. The issue with the cover, on the other hand, does make the book unpostable I believe. Taping a cover that has been ripped off (or even just ripped more than one inch) does not magically make it postable again. I would mark a book in that condition received with a problem and ask for my credit back.

Yup, there can be no rips in the cover larger than 1 inch. Taped or not.

Bends, folds and white lines are not disallowed, although like Liesl says, if they are excessive, then the book may fall under the "excessive wear" rule.

You should ask for your credit back.

Here is a link to the rules for postability of books: http://www.paperbackswap.com/help/help_item.php?id=205#

Absolutely ask for your credit back. When I first became a member, I got a couple of unpostable books that I didn't mark RWAP because the damage wasn't too bad and I felt for the senders of those books. I should have asked for the credits back because this site has standards and I'd have been doing a service to the other users of PBS if I had called them out on sending unpostable books here.

Just this week, I've received three unpostables (one with extensive underlining, two with water damage) and you can bet the I marked them RWAP and asked for my credit back.

Also, remember that they need to send you another credit if the sender wants to get the book back. So the sender would be out two credits and postage for sending out a book that is not up to standard. I'd imagine that it should be an incentive to only post books that are up to standard.

You were sent an unacceptable book.  I think it's okay for reading but you are not going to be able to repost that book.

Thank you so much for the advice!