Personally, I love playing against players who have no idea about the math. They may suck out on me from time to time, but over the long run it's +EV for me!

But, I think Caro is being disengenuous. From what others have said (since I'm playing micro limits and NLHE MTT), I'd have to say as the limits increase, almost everyone has an intuitive grasp of the math involved and playing the player (or psychology as Caro puts it) becomes much more important. I think there was loads of this type of info in Theory of Poker.

edit: I'll also be honest and admit I can never finish any book by Caro. I do have his book of tells on my shelf, but havent read it yet. I've tried to read two others and put them down rather quickly. So maybe I'm biased.