Hi ddb1990,
To start, a 640 is a really strong initial CAT score (the average score on the Official GMAT hovers around 540-550 most years). As you continue to study, and take more CATS, it's important to take those CATs in a realistic fashion (so take the FULL CAT - with the Essay and IR sections, at the same time as your Official GMAT, etc.). You have a strong Verbal ability, which is good. There are actually a variety of different score combinations that will get you to 700+, but since Business Schools tend to place extra emphasis on an applicant's Quant Scaled Score, you'll likely want to spend more time on that section of the GMAT than on the Verbal section.
There are a variety of resources that you can use during your studies, so you can certainly begin with the ones that you've selected. However, you have to be flexible enough with your thinking to adjust your plan as needed - which might mean adding some new, non-book resources. To that end, you should plan to take FULL-LENGTH CATs at more frequent intervals than you've currently planned to. You should take a CAT every 1-2 weeks (or so).
1) What Schools are you planning to apply to?
2) When are you planning to apply?
GMAT assassins aren't born, they're made,
Rich