The only prep material you need

The Manhattan GMAT prep set was the only resource I used to study for my GMAT. The discrete guides were a great way to really focus on your weaknesses. In general, you want to avoid spending too much time on things that are already strong on so I truthfully read about half the books in depth and skimmed the other half.

Additionally, the practice pad was instrumental in getting my score squarely above 700. I would attribute a good 20 points to proper pad management - setting it up ahead of time and using it to help manage time.

Additionally, the teaching content of the guides were great - the GMAT is a game and the MGMAT materials treats it as such - it gives you the strategies and trains you to know how to play the game. You don't need to genuinely understand or know the content intimately to ace the GMAT - you need to know how to play the game.