There doesn't seem to be anything about bent books in the condition guidelines. I usually assume they're unpostable. What do you think? Does it matter if it's a slight bend just at the top or bottom or a more significant bend?

are you referring to a bend in the cover?

IMO, unless the bend has resulted in damage to the pages, I think they are postable.  I've received several that have been almost been U-shaped but they flattened out okay after I stacked heavy items on them for about a day or so. 

I mean the book itself is bent, not the cover. Like I have one now that's kind of an S-shape.

Personally I wouldn't post a book that is eithre "U" shaped or "S" shaped (that one I'm interested in what it looks like) - don't think I've ever seen an "S" shaped book.  LOL. 

Don't think I'd like to receive either shapes though, but one slightly "U" shaped probably wouldn't matter.  Just MHO.  Pat

An S shaped book?  Yeah, I'd like to see that one!  I am thinking that that sort of crazy configuration would make it unpostable, under the general "needs to be in decent shape" condition.

S shaped sounds pretty weird:P  U shaped bends would depend on where the bend was, but book weights might straighten it out.  If it's a vertical bend, I'd try putting it on a hard surface with the fold or base of the U facing up, and then put a couple of very heavy book weights on it.  If you don't have them, a large hardcover book with something heavy on top of that will work.  Just leave it under there overnight and see how it looks the next day.  I bet that even if it doesn't lay perfectly flat & smooth after a day or two, you'll still end up with something in postable condition.  It's worth a try anyway.  Horizontal bends though, might be something else.  If the spine gets too weakened or broken across the middle, I don't think there's much that can be done for it.  This one sounds like it got packed away badly or smooshed up in a drawer.  I'd try the book weights and see what happens.

I received a book that the sender used a rubber band to bind it in shipping. The rubber band was too tight and bent it in all sorts of weird ways. It was nearly crumbled- but in like new conditoion otherwise!  I accepted the book then informed the sender that they might want to stop using rubber bands!

I don't post books like this. I call them warped. My 12yr old daughter has a bad habit of bending books so the cover doesn't lay all the way flat. She'll have a book in her hands and kind of hold it so it looks like a rolled up newspaper. The book will meet all of PBS conditions, but still I wouldn't want to get a book like that.I often get onto her about it since she likes me posting her books, but still it's habit that is hard for her to break.

I Never thought of putting something heavy on it though to correct it. I'll do that.