In the market for A4 paper, Conrad is just one of many producers. A4 is a standardised product, and it doesn’t require major investments in research and development. Life as a producer in such a market isn’t particularly complicated. If you keep your costs under control, you simply produce up to the point where the cost of making the last sheet equals the market price. In contrast, as the publisher of a new textbook in microeconomics, Alpha Books enjoys a monopoly position. A monopolist has the power to set a price above marginal cost (MC), but this power is not unlimited: if the price is too high, customers may switch to another book or buy a used one. Life as a monopolist isn’t especially complicated, but it does involve more considerations than under perfect competition. Not only must you keep an eye on your costs, you also need to think carefully about the demand side to find the optimal price. Life as an oligopolist is much more complex, and there isn’t one theory to describe all situations. In this chapter, we will present the three main oligopoly models.