WASHINGTON – Horse racing has rarely inspired serious fiction. Novels about the sport are usually formulaic (e.g., Dick Francis’s mysteries) or filled with cliches (e.g., the triumph of an underdog.) So it was a shock when “Lord of Misrule,” a new novel set at a bottom-level West Virginia racetrack in the early 1970s, was named one of the five finalists for the National Book Award for fiction, a prize that has been won by literary giants such as William Faulkner, John Updike, and Saul Bellow.