Check to see if your law school has a recommended reading list. But don't spend the entire summer doing nothing but reading books off it. Enjoy what time you have left because you won't be reading for leisure in a few months.
That being said, I agree with most of the other posters. Law School Confidential, One L, Buffalo Creek Disaster, etc. were all good reads. In fact, I still have most of the books I read from our recommended reading list.