We test the Coase Conjecture by noting the prices of a sample of online books on the day that they were released. To determine marginal costs of online books, we observed prices of books whose copyright had expired. For our sample, initial prices were not even close to marginal costs—the median price was more than ten times marginal costs. We document other empirical regularities that often contradict many existing theories about durable-goods monopolies. We conclude that the theories that best explain these regularities are ones–such as those of Stokey (1979), Sobel (1991), and Board (2008)—that assume that a monopolist can commit to a schedule of future prices.