Manhattan Prep is the way to go!

Manhattan Prep is the way to go for GMAT. I bought Manhattan GMAT books after reading their excellent review online; however, I was still lost after reading through all the books. I then signed up for 9 week course online with Manhattan Prep and that was definitely money well spent. The classes are incredibly helpful and both of my instructors, Ryan Jacobs and Paul Fisher, were really knowledgeable and approachable. They teach you so many tricks that you would never learn by just reading the books!

After taking the classes, I found that I was still struggling with CR and certain areas of quant. I then took 4 private lessons with Ryan that essentially helped me to cross the 700 mark.

Ryan is an awesome teacher who genuinely cares for his students and is always available to answer questions, even when he is on vacation. If you are struggling with GMAT in general, I suggest signing up for classes with Manhattan prep. However, if there are specific areas that need work, I would sign up for private lessons (they are expensive, but so worth it). If you can, I would recommend taking a class with Ryan. He will make them fun and really work with you to understand the deficiencies.

A big thank you to Manhattan Prep and Ryan Jacobs!