I bought some books from Nerdbooks and found the experience a good one. I put the order online by 12.30 or 1 pm and got a call from them by 3 to confirm the order and the books were shipped within a few hours. The books reached me by the second day along with a free T-Shirt. The packing was excellent and the books was in top condition. They usually give a discount 10% to 15% better than Amazon.
If you are planning to buy books online, I strongly recommend Nerdbooks.