I like to use the Barnes & Noble membership coupons to get deep discounts on various books. I go to the Sumter Landing B&N a few times a year to buy books at sometimes at a 40% discount with a 15% discount on top of the 40% but taken on the 40% discounted price.

I try to use the actual store rather than the online version because of the Shipping and Handling.

For online purchases, I like United Kingdom's The Book Depository as they do not charge any Shipping and Handling (from the U.K. too). In addition, the Book Depository has deep discounts on many books and other items. http://www.bookdepository.com/