Hi cgreenatl,
I started learning with the Manhattan Strategy Guides and I can say that they are really good in teaching you all the strategies used in the GMAT. On the other hand, they are also quite detailed, which might be not that good, if you don't have that much time. Over one month of prep time is still quite a bit of time, of course depending on how much time you can devote on studying each day..
I just worked through the Number properties, Equations (,...), and Fractions book.
The Equations book was great with a lot to learn, number properties provide a good fundament as well, the fractions book got some neat tips as well, but maybe not that fundamental (as long as you know in general how to handle fractions).
So if you are somehow fine with the verbal part, I would advise you to fast buy the Equations book. Than you can also access all 6 CAT Manhattan exams. Try some of their exams to get a more realistic score. If you work through the book and like it, then go on and buy the other guides, where you still see problems!
From what I see, the Words translations book also seems great as it might be the closest to prepare you for real questions (while the others provide you with the skills you need).
For the verbal part, the SC book is quite fat and i guess it takes quite some times to work through (and still remember the concepts). Anyhow, in my opinion, for the verbal part, training is the best... okay maybe for SC you need to know the rules.
BTW, was one of your Kaplan score from the linear test? I just purchased a Kaplan book and did (unknowingly) the linear online test. How comparable is the linear test score to the CAT test score?
Cheers,
Tobias