What can I expect from a 590 base score?

Well, being realistic, I would say that if you're starting at 590, a 750 is probably not a wise target. That's an enormous jump, and very few (less than 5%?) of test-takers hit 750 at all. 700 may be doable if you're diligent, especially since you'd only had 3 hours of prep before the first test.

You've got the right books for the most part...start with the strategies in the Princeton Review book. Do practice questions in the OG, one question type a night. Take full tests on the weekends.

You didn't say, though, which test you took. If it was Kaplan, then ignore the score. They're way off (which would be a positive, because Kaplan scores much lower than you really would). If it was Princeton Review or GMATPrep, then it is a pretty reliable score.