Though Christopher wrote about many sports, his most frequent subject was baseball. His best baseball books are considered to be "Wild Pitch", "Catcher with a Glass Arm", and "The Kid Who Only Hit Homers". He also wrote many books about football, including "Tough to Tackle", "Crackerjack Halfback", and "Football Nightmare", and soccer, including "Soccer Scoop", "Soccer Halfback", and "Top Wing", basketball and hockey. He has written books centered on snowboarding, dirt bike racing, volleyball, golf and many other sports, in addition to a number of biographies of sportsmen and women. His first children's sports book published was "The Lucky Baseball Bat", a 123-page novel published with illustrations by Robert Henneberger by Little, Brown of Boston in 1954.