Author of the book Moneyball, Michael Lewis is not primarily a baseball author. He started out as an investment banker, and then went into writing books and magazine articles on a variety of topics. His earlier books on non-baseball topics have often been best-sellers. Notable, among others, have been Liar's Poker in 1989 (about investment banking) and The New New Thing in 1999 (about Silicon Valley).
A lengthy interview with Lewis about the book Moneyball appears here: