Hi fragrance,
The problem you're describing actually happens to many Test Takers who use a "book heavy" study approach. 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. Depending on your current ability level and your goal score, to make a big improvement you'll probably have to change your study approach. This will likely mean investing in some new Computer-based resources and learning (and practicing) new Tactics.
1) How long have you studied?
2) What materials have you used?
3) How have you scored on each of your CATs (including the Quant and Verbal Scaled Scores)?
4) What is your goal score?
5) When are you planning to take the GMAT?
6) When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich