Up in Evanston, Illinois, there's a used bookstore unlike any other I know. At Market Fresh Books, books are sold by the pound. I'm not kidding - they're $5.99 a pound. It's a unique way to sell books, and it's really fun.
The Market Fresh collection is pretty big, and includes extensive sections for fiction, kids books and cookbooks. As Evanston is the home of Northwestern University, it's not surprising to find a large collection of used textbooks, too. Not sold by the pound, but also available are DVDs/CDs, and comic books in addition to City of Evanston and literary t-shirts. There's a decent romance section, though it was pretty picked over when I was there. All I came away with was one Sophie Jordan Avon Romance. (I didn't find any Gail Carriger, but she tends to be an author whose books don't wind up being re-sold very often.)
Aesthetically, Market Fresh is located in an old storefront. It's a little run-down. It's a used book store, after all. However, that doesn't detract from it's charm. Visiting is a bit like going on a treasure hunt. You just have to be willing to dig a bit.
Visit Market Fresh Books and see for yourself. While you're in the area, you're in walking distance to the Evanston Barnes and Noble, the Public Library, and Bookends & Beginnings (now in the space formerly occupied by Bookman's Alley). Also, I can't speak highly enough of Smylie Brewing Company, which is just a couple blocks away. Spend an afternoon in Evanston, and you can get a serious book fix.