Boomer and I try to make it to at least one baseball game each season. It's so fun to take the train to the stadium and chow down on some garlic fries. Oh yah, and watch the game!
This is a very straightforward and easy-to-read guide to the game of baseball. It covers the field, the players and their positions, scoring, and even a chapter on how to dress appropriately for the ballgame (which is basically: don't wear the other team's color, and wear sunblock!).
The most helpful chapter for me was on how to read the box score.
If you're new to baseball, or want a refresher course, pick this up.