If nothing else, Quantum Books is a compelling alternative to the mainstream bookstores. They stock an eclectic, mostly technical mix, but their major draw for college students (like this reviewer) is the cheap textbooks.
Here's the thing: Quantum will get your textbooks cheaper than the campus bookstore, but it can never beat secondhand reselling. If you want a good deal on a new book, go here. If you like the atmosphere, go here. If you love supporting independent, local business, absolutely shop here; it's a nice place!
But the most spendthrift grad students will find a better deal eight times out of ten.