At one time I wanted to be an accountant, but after a few attempts at taking classes and studying the books, I couldn't take it. The books always put me to sleep. Poker books, on the other hand, don't have the same effect on me. I find them very interesting, and the more I play, the more useful the books are. You need to play and study; either one on its own won't allow you to progress fast enough. Think how hard it would be to become a good accountant without studying the material in the books but just making entries in your journals. Likewise, if you just read accounting books and never tried to apply it, you wouldn't be an accountant. You have to do both. I think Poker is the same way.
Poker math is about odds, and if you don't know the odds, you're bound to make mistakes -- and that's the goal of good poker players, to induce mistakes from your opponents and avoid making them yourself. If you go against the odds, in the long run, you will lose.