HALF.COM is the best site for textbooks HANDS DOWN. One semester I had to buy 10 books. I spent $40 including shipping on half.com. Bookstore would have been at least $250.
But are you talking like textbooks for Disney classes? If you have to buy a book, then you can find it at the Virgin Megastore quick and not that expensive. (The only book for a class that I had seen was "what color is your parachute" but that could have changed)