I thought this was far and away the best USMLE Step 1 Question book out there. It covers conceptual, high yield, board relevant material without going into the preposterous minutiae that a number of the question books out there are notorious for. The accompanying CD is excellent, and you can test yourself by system. There were some minor gliches in the CD, but these did not detract appreciably from the overall quality. I had the highest USMLE scores in my class, and I do think this book helped with that.