From the wild swings of the stock market to the online auctions of eBay to the unexpected twists of the world's post-Communist economies, markets have suddenly become quite visible. We now have occasion to ask, "What makes these institutions work? How important are they? How can we improve them?"

Taking us on a lively tour of a world we once took for granted, John McMillan offers examples ranging from a camel trading fair in India to the $20 million per day Aalsmeer flower market in the Netherlands to the global trade in AIDS drugs. Eschewing ideology, he shows us that markets are...