A dandy, in-depth look at the Sport of Kings, the $10- billion-a-year horse-racing business, and the ``weekend recreational gamblers,'' jockeys, trainers, grooms, and officials who work on the ``backside,'' behind the scenes. The appeal, according to Helm, a San Francisco journalist and publisher, ``is that it is the most complex and interesting form of gambling.'' But there are also the fabled traditions of the sport, the entertainment factor, and the camaraderie that draws a varied audience. Helm's trackside cronies include a chef, a blues critic, a ``street artist/grant hustler.'' a mail marrier, a retired black woman, and a wine salesman. It's the grandstand kibitzing, the arguing over horses and jockeys and odds, as much as their occasional winnings, that brings them back to the track. Helm became interested in the daily operations of Golden Gate Fields and Bay Meadows and gained access to the morning workouts on the backside, a world he learned was like a ``small medieval city'' with its own language and traditions. His lengthy interview with jockey ``Cowboy'' Jack Kaenel, who won the 1982 Preakness on Aloma's Ruler, reveals the finer points of a demanding profession. Helm delves into the arcane mechanics of horse-racing, such as the difference between ``claiming'' races, derbies, stakes, and allowances, and the weight and equipment requirements. But at the heart of the book are his profiles of trainers like Chuck Jenda, whose mounts have won an astounding 20% of their races; of the track superintendents, who attempt to maintain consistent conditions in all sorts of weather; of the veterinarian whose individual judgment decides ``racing soundness''; of the ``powerful, but largely anonymous'' stewards who are the arbiters charged with ensuring the ``integrity of racing''; and of the racing superintendent, the ``matchmaker'' who is like the ``director of a theatrical event.'' A sure thing for novices, but there's enough intelligently presented information and inside dope to attract even the most jaded track veteran.