I'll throw in my advice:
I think buying review books early is a bad idea. From what I have seen, when students have review books in hand as they first learn the med school material, they tend to spend too much time "reviewing" the random factoids for the Step exam, rather than actually mastering the concepts of the material they are studying.
It's worthwhile to keep in mind the difference between your course exams and the Step exams.
Course Exams: Requires detailed mastery of specific topics, ability to extrapolate from material you have previously learned, in-depth examination of subjects
Step 1: Requires you to regurgitate specific facts and recognize patterns
The skills required for each are fundamentally different. I had more than a couple classmates fail course exams because they spent too much time reading First Aid, and not enough time in the basic texts.
Truthfully, my course exams were far more difficult than Step 1. The only reason Step 1 is so brutal is because of the volume of facts you are expected to recall. It is not conceptually difficult at all.
I believe that, especially in 1st year, you should stay as far away from the review books as possible, because what you should be doing is learning the material in depth, while review books focus on superficial issues. You're not going to learn Pharmacology fro Kaplan, you're going to learn it from Goodman. "Review" books are called that for a reason.
I waited until two months into MS2 year before I picked up the review books. I got a copy of the Kaplan Lecture Notes (expensive as hell on Ebay, but still cheaper than the damn course), Robbins Review of Pathology, Lippicott Pharm, and a whole mess of practice question books + Qbank + USMLEWorld. I got >240, so maybe what I'm saying works.
Just my 2 cents.