georgepaul0071987
Also there's no overlap between the OG quant/verbal review and Gmatprep right ?
If we're talking about the most recent versions of the OG material, then there is no overlap.
It seems that you're worried about exhausting all of your question resources too early. Don't worry, that won't happen. After you finish the three OG books, there's still lots of high-quality questions out there to use. The
GMATClub tests and Sackmann's math sets are two examples for quant, and for verbal there's LSAT questions for CR and RC. Along with the GMATPrep software and practice tests from Manhattan, that's plenty of practice material available.
Another issue is to not get too bogged down with the OG material. The OG is essential, so by all means answer and fully review every question and explanation. However, it's not that great in terms of preparing for upper-level questions. Once you successfully complete the OG, move on to more advanced material.