Chapman and Maclain Way’s energetic telling of one of baseball’s great, unheralded stories is as much about independent spirit as it is about the game. When Portland, Oregon, lost its longtime minor-league affiliate, Bing Russell—who briefly played ball professionally before enjoying a successful Hollywood acting career—bought the territory and formed a single-A team to operate outside the confines of major-league baseball. When they took the field in 1973, the Mavericks—the only independent team in America—started with two strikes against them. What did Deputy Clem from Bonanza know abou...