When Coca-Cola offered the first retail coupon in the 1880s, customers were thrilled. But today, one in four American shoppers will buy something only if it's on sale, and almost half of all merchandise carries a promotional price. The relentless pursuit of deals has totally disrupted the relationship between buyers and sellers. In this playful, well-researched book, journalist Mark Ellwood investigates what happens to markets when everything's negotiable.