Need math help!

[Rushmore]

There, I said it.

That's the first step.

Anyway I have a lot memorized, of course. But what I'm looking for is a simple text for understanding probability a little better. It doesn't have to be for poker, per se. In fact, it might be best if it weren't, unless there's a definitive text. For instance, I have The Holdem Odds Book, by Michael Petriv, and it's all about memorization, which is fine for that. I want to be able to get it all down myself on the spot.

Yes, I realize this should be in the Books and Software forum, but I figured I'd get a better result here.