Wolmar, a train enthusiast -- he calls them "certainly . . . the most important invention of the second millennium" -- has written an animated account of the history, evolution, and economic, social, political, and military significance of railroads since their invention in the 1820s. He gives main billing to their importance in continental Europe, the United Kingdom, and the United States. But he does not neglect railroads elsewhere, including the politically motivated and technically challenging Trans-Siberian Railroad and those that transformed British India. Passenger traffic began to decline in rich countries in the 1920s, as cars provided stiff competition and governments neglected to modernize railroads. Provided governments make the adequate investments, Wolmar foresees a train renaissance in the twenty-first century, driven by high and volatile oil prices, increasing urban congestion, and technical improvements that permit faster and more comfortable trains.