To habitu s of the nation's top racetracks he's known as "The Bland Buddha of the Bangtail Circuit." Less polite players of the ponies call him a tout or a bookie. There's no doubt that Mr. Joe Maddox is a shrewd judge of horseflesh, but he's also a shrewd judge of men. And that's a critically important quality to possess, because Mr. Maddox repeatedly finds himself pitted against crooks and killers whose depredations are linked in some way to the...