At my school, at my first year books were all required and we used everyone of them. If you have a writing class, you may be able to get away with borrowing someone's or waiting to see if you really need it. But I wouldn't advise waiting...get all your case books and other required stuff.
What I do now is buy all of my books at campus then buy them online again used, and then return them to the bookstore once they all come in. Waiting for a book to be shipped sucks, especially when you need to be prepared for 1L classes.