I see some others saying that math is not that important when your opponent doesn't understand the math, but isn't that an ideal situation? Isn't it most profit generated by causing your opponents to make mistakes?
Knowing the math gives you the opportunity to make the most out of those situations. Sure, some idiot is going to make the wrong call and win once in a while, but most times they will lose, and you take their money. Isn't that the basis of how
casinos are run? By having players play games with a negative
expected value? Eventually someone hits a jackpot and walks out with fists full of cash and brag about that big score, but I bet the house still finished the night ahead.
But back to the real topic, Chen's book is great for math. Harrington on Hold Em also has some decent tools to use.