Highly Recommend

I'd highly recommend Manhattan Prep, and specifically Marcus Hedahl as an instructor. I improved over 100 points from the 600's into the 700's from the beginning of the course to test day in a little less than three months.

Manhattan Prep has the GMAT down to a science, without a question. (Not to mention, the customer service is incredibly professional, responsive, and all-around very helpful). Specifically, Marcus knows the exam backwards and forwards, and has tips, tricks, and invaluable insights into how to approach the exam, which I imagine are unparalleled among other prep companies. He also makes each class fun, lively, and engaging, which makes a real difference with a 3 hour class after a full workday. He's patient with everyone in the class, and has really great advice on how to approach various question types, common mistakes, study habits, and generally anything at all related to the test. I really can't speak highly enough of Marcus.

I would recommend focusing less on strategy books and more on practice problems, but as far as prep companies to use, Manhattan Prep is undoubtedly the way to go.