Can't quite tell how you are going to go about it, but it seems like this type of venture might have the best shot of working by focusing on a single campus at first. A lot of groundwork marketing to social organizations, academic clubs, whatnot in order to try and build a local community whose needs overlap to prove the model and then scale out. Focusing on a single campus or two would make the "ball rolling" phase much more achievable as well.
Also getting going before finals week when everyone is selling books for beer money so you have an "inventory" for the next semester or investing some money in common textbooks yourselves to lend out to get the ball rolling couldn't hurt.
Site wise I can't really see much as everything seems to route back to the home page. I'd say your tag line could use an edit - "Cheap college textbook rentals just got better" isn't really a call to action or very descriptive of what the service the site preforms.
Good luck!