Book excerpt: Every year, U.S. casinos give away more than a billion dollars worth of amenities to customers in return for their gambling action. These giveaways, known as "comps" (short for complimentaries), range from parking and drinks to gourmet meals and airfare. Are you getting your share? From nickel slot players to $500 a hand blackjack high rollers, Comp City has shown tens of thousands of gamblers how to get free casino vacations.