it is what it says, a great way to exchange books with strangers. It's a point based system, you get 2 starter points for signing up and listing 10 books you're willing to swap. For every book you send out (you pay postage) you get a point. For every book you request sent to to you (they pay postage) you spend a point. Ends up to be $2-3 per book, which is about what i pay at Goodwill.
Get free books at this book-swapping site. (Not just paperbacks.) Great way to get rid of your own library over-flow or request books for yourself. Each time you place a book with someone, you receive a point. (One point = one book.) Very well organized and there's an endless selection of books from which to choose.