Hi Surbhisharma,
Based on what you are asking about, it sounds as though you are planning for a "book heavy" study routine. Unfortunately, many GMATers who study in that way end up getting 'stuck' at a particular score level. Even the best books are limited in what they can teach you; they also can't force you to approach questions in a certain way and their explanations are often one-sided. As such, you would likely find it beneficial to invest in some new, non-book study materials for this next phase of your studies.
Since you have finished the Official Guide, have you taken any practice CATs/mocks yet? Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How long have you studied? How many hours do you typically study each week?
2) Which version of the Official Guide have you worked through? Have you used any other study materials besides that one book?
3) On what dates did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
4) What is your overall goal score?
5) When are you planning to take the GMAT?
6) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich