If you go through this link here, you can get free standard shipping and an extra 5% off your order. You can also use code T9J9B3Y to get $2 off your order or 10% off one item. (Not sure if you can combine the code with the Visa offer or not.)
There is also currently a Buy 2 get 1 free on bargain books here.
Combining the Visa and B2G1 offers, you can get a pretty good deal on some books. Since I don’t have a VISA card I can’t test it out. So let me know if it works!