Timothy Ferris provides a clear, elegantly written overview of current research and a forecast of where cosmological theory is likely to go in the twenty-first century. He explores the questions that have occurred to even casual readers -- who are curious about nature on the largest scales: What does it mean to say that the universe is "expanding," or that space is "curved"? -- and sheds light on the possibility that our universe is only one among many universes, each with its own physical laws and prospects for the emergence of life.