I used the USMLE Step 1 review book (basically due to lack of a better option), Lower Limb Anatomy notes (which were far more detailed than required on the test), Pathophysiology Made Ridiculously Simple, and notes from a few classes (Pharmacology, Neuroanatomy, Biochemistry, etc.).
The test is designed so that many people will get a lot of questions wrong so that they can scale it to where a certain number of people pass. If the test was easier, they wouldn't be able to scale it backwards (to make some people, who did well, fail). Hence, the test will always seem very difficult.
Certain schools will prepare students better than others (as evidenced by a history of pass rates), so if you go to a school (and that could be any of the 9) that doesn't have a great pass rate history, you might need to go above and beyond in the studying. Just something to consider. Hope this helps.
DMU 2012