Hi Nick,
Many Test Takers are unhappy with their initial practice scores, but you really shouldn't be. That initial Score is just a measure of your skills right now - and you'll improve on that result over time as you learn more about the content, Tactics and little 'secrets' of the Exam.
From what you describe, your immediate study plan is 'book heavy'; unfortunately, many Test Takers 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. There's no harm in starting off your studies in that fashion, but you'll likely end up needing to invest in some additional, non-book resources at some point.
Before I can offer you the specific advice that you’re looking for, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How much study time have you put in so far?
2) How did you score on that initial CAT/mock (including the Quant and Verbal Scaled Scores)?
Goals:
3) What is your overall goal score?
4) 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