Well, if you're talking about prereading before classes, don't even think about it. You will start out with biochem and population medicine, which are pretty easy. If you preread a day or two before each lecture you'll be doing far better than most (I don't know anyone who consistently does this). But really, they do start you out slow and you don't need to worry about reading anything at this point.
That being said, once the quarter starts, some people do prefer to rely mostly on the syllabus and others (like me) like to use books. They will give you a book list before orientation starts that contains "required" and "optional" books for each course. Now, really there are no required books, because everyone will follow their syllabus. The required book for biochem is Lehninger's 4th ed. I didn't buy it, but did use the excellent Lippincott's Illustrated Review of Biochemistry (really halfway between a brief textbook and a review). The syllabus for biochem is generally excellent as well.
For population medicine, some of the lectures were pretty confusing and the syllabus is of varying quality. I read the assigned book "Clinical Epidemiology: The Essentials" by Fletcher, which was extremely clear and very short. I highly recommend it.
For genetics the syllabus is sufficient.
Also, the BRS Biochemistry book is a good source of review questions if you find that helpful. Someone will be selling a CD called M1 Oracles that has old (very old) exam questions, which are more or less useful depending on the class and whether you like doing questions.
There, that should get you through til anatomy starts