If it is in First Aid, it is on the Step 1 exam. PERIOD. I found Kaplan to be good, but a little too much. That said, I am glad I went through it cover to cover. Don't forget Q-bank. That was probably the most useful tool for me in step 1 prep. If you make it through the first two years, you already know the material. Go light. I also used Gilligan case studies in Micro.
The Kaplan books for live lecture were extremely helpful. first aid is NOT ENOUGH! unless you already know all the information; even so, it is useful to keep notes in your first aid book from the kaplan as the main source.