http:/www.gohastings.com

5 used books for $20.  I did it twice.

The books have to be under $29,99 MSRP.  They have to be in stock.  They have to be used.  You have to get 5.  You also have to pay shipping and tax.

Shipping for me was ~$6 on each order.  +~$2 tax. 

= ~$28 for 5 books, which is ~$5,60 for each book.  Not too shabby.

You don't need a code.  You should see the shopping cart price go down to $20 when you add the fifth eligible book.

I could have made two more orders, except several books I've had my eye on were already out of stock. :(

Order early, I think, before ALL of the good stuff is out of stock.