Oh god no. Please enjoy your summer. Even if you asked the faculty at your medical school, I'm sure they'd say use the summer to relax, spend time with friends and family etc. Once you start, they'll teach you the things you need based on their own course structure. Reading a medical textbook now won't be of much help as the material either won't make sense and you'll probably forget a lot of what you've read by the time you start uni as it will be very fragmented learning.