The Book Hive is a wonderful used bookstore located in New Hope (off 36th & Hwy 169). Like many used bookstores they give you credit for books brought in and you pay 50% of the list price to buy.
For me, what makes The Book Hive a place to shop is the service (ALWAYS very helpful!) and the selection. They are a huge shop with many titles, from kids' books to DVD's even. They will locate books for you if it's not on the shelf.
The only problem I have has with them is I have received less than credit due on some books I brought in on one trip there. I now try to go there when William is working. :)