The best thing you can do is to do the practice tests. This familiarizes you with the wording and timing. Keep in mind that the Chem, Bio, and Math sections test you over about 10 prerequisite courses alone. There is no way if you don't already have a really good basic knowledge of the subjects you will improve drastically by reading a book. But the Kaplan book should be as good as any. I looked at it for statistics and anatomy since I hadn't taken them. Not sure how much it helped my score much though. I think my score would not have been in the 90s had I not done the practice tests.