Hi akiara,
About 10% of GMATers have been scoring in the 700-800 range over the last 2 decades BEFORE that particular book was ever produced - so the answer to your immediate question is that working through those practice questions isn't particularly important to that Score Goal. With a Q46 and a V36, your particular "needs" are NOT about correctly answering advanced question; you need to change how you 'see' (and respond to) the overall Exam.
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 in total? How many hours do you typically study each week?
2) What study materials have you used so far? What “brands” of CATs/mocks have you used?
3) On what dates (or approximate 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 apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich
760+: What GMAT Assassins Do to Score at the Highest Levels