Levathes, a former staff writer for National Geographic, tells the tale of Chinese emperor Zhu Di and his favorite eunuch admiral, Zheng He, who tried during a 30-year period to break China's isolation with seven major naval expeditions to India, Indonesia, and Africa. Levathes writes popular history and therefore sprinkles her text with scene-setting and little digressions into everyday life in Ming China. The descriptions of the giant naval docks at Longjiang are fascinating, as is her account of the eternal intrigues between the eunuch faction and the Confucian bureaucracy at court. The eunuchs and merchants wanted trade, exploration, and capital venture; the Confucians wanted moderate taxes, isolation, and priority given to agriculture. The struggle between these outlooks dominated -- and still dominates -- China's dealings with the outside world. Zhu Di was with the merchants, and his fleets were veritable mercantile armadas, with boachuan (treasure boats) 400 feet long. Their principal destination was Calicut in Kerala, the only state that the Chinese did not regard as barbarian. From here they brought back spices, elephants, and the first eyeglasses from Venice. Having established Chinese domination of the Indian Ocean, Zheng seemed to be on the brink of ushering in an era of global Chinese imperialism and openness to the outside world. It was not to be. Zhu Di died in 1424 and was succeeded by his son Gaozhi, a devout Confucian who banned all naval voyages. A hundred years later, China had no navy and anyone caught even sailing on the high seas was summarily put to death. Levathes illuminates a historical crossroads: the century in which Western and Chinese expansion overlapped. She does not fully explain why one continued and the other did not, but she does expose one piece of the historical jigsaw puzzle, namely the root of the Chinese inability to open a door to the outside world. She does this entertainingly and with a minimum of dry analysis.