I'm always amused by people who are so concerned that their books "look right". Because what's important is how your books look on the shelves. Yes, book club editions look different from the hardcovers bought in a store. If it's so important to you that you have a retail edition instead of a book club edition, why don't you, I don't know, pony up the money to buy it yourself instead of mooching one out of a swap site?
I've gotten books through swap that haven't been in the best shape. They've been ex-library copies, missing dust jackets, or have worn spines and bent covers. But I'm not expecting a pristine retail quality book from a swap site. It's a free book. I just want a reading copy. If I like the book enough, I'll keep it, and if I don't, I'll swap it right back out the door. Not once does it come into my head that the book needs to "look right" next to my other books. I guess I'm more concerned about what's in the book than with impressing people with my impeccably arranged by size-and-color shelves.
I like used books. Used books are fun, especially when the previous owner has left a little something of themselves inside. Kids' books usually have a name childishly scrawled inside the cover. One book I got through swap was actually autographed by the author (and was apparently signed to a woman and her cat, which is just... sad). And one I'm reading now still has the original receipt inside--it was bought in an airport in New York (and their sales tax is lower than it is here wtf). Little tidbits like that are really interesting to me.
Yet I take care to make sure nothing of mine is left in any of the books I swap out, because I'm weirdly private that way. It's bad enough that they're getting my name and address on the return label.