I heard that when you read a book in order to prepare for the exam, you always sleepy. And I think I can help you.
When you know the exam when you may have read the daily 20-30 minutes before going to bed. To prevent drowsy or if you have time to read a lot and you may take a nap for a 10-15 minutes. For the body to rest a bit. When I wake up to see it clear A good memory and the last before the exam room may be your friends who study well review.