I used First Aid for Step 2cs. It's an easy read and will take you 1-2 days. The most important parts are the beginning chapters which explain the format and grading of the exam, and the 25 or so practice cases in the back (which also have an 'answer key'). I had a few cases which were almost identical to the practice cases. If you have a buddy or S.O. to practice 1 or 2 cases on, it would probably be helpful just to get a feel for time constraints (especially note writing). Always remember to wash hands, drape the patient, put the stethoscope on skin, and be empathetic.
However, all of this is just to help with your anxiety levels. If you speak English, are fairly empathetic, and can write a decent SOAP note (with 5 DDx and 5 daignostic work-up's) you will be fine. I would spend a week, max, studying for this exam.