Moneyball: The Art of Winning an Unfair Game by Michael Lewis is a baseball story on the surface, but it is much more than that. The theme that surfaces is that things and people are not always what they seem to be on the surface, and the underdog can be a winner in the right circumstances.
The story revolves around Billy Beane, a former underachieving baseball player, who became a successful manager for the Oakland A's the year they won the Western Division Championship. Billy was a much touted player who was drafted right out of high school but he failed to live up to his intended potential on the field. It is when he becomes a recruiting manager that he is able to successful build a team with "misfit" players at bargain prices. Billy was competing for players in a market that demands high salaries and big contracts, neither of which the A's could afford. Beane signs players who were let go from big name teams like the Red Sox for much less money. This group of players makes a collective effort and ends up being successful enough to win the Western Division championship.
It is Billy Beane's style of recruiting the underdog that, on the surface, seems like disaster waiting to happen, but proves to be lucrative for the team. Things are not always what they seem.
The theme of the book is how a small-market team that can't spend the same amount of money as other teams with large payrolls can be a winning team by using a specific formula as opposed to spending millions of dollars on the best, most high-profile ballplayers in the league.
The statistical methods they use incorporate which players get on base the most, rather than who has the highest batting average, who hits the most home runs, etc. It's about taking on athletes that other teams disregard because they have a weird pitching motion or they have a history of injuries.
The book follows Billy Beane, the GM of the Oakland Athletics after his team loses some of its biggest star players to free agency because they can't afford them. They go on to winning more games than anyone expected with a roster of players, none of whom are stars, that work together, work the pitch counts, play hard, and play good, fundamental baseball.