Carl Sagan was without question the most famous scientist since Einstein. This biography tries to show why. Born to a Brooklyn Jewish family in 1934, Sagan showed an early interest in stars, dinosaurs, and large numbers: typical for a bright youngster. Later, he began to read science fiction, did experiments with a chemistry set, and dreamed of a career in astronomy. After persuading his parents he could make a living looking at stars, Sagan attended the University of Chicago. There he laid the foundations for the work for which he would become best known, acquiring influential mentors and writing a doctoral thesis with the unstated theme of life on other planets. Within a few years, he was among the leading experts on the subject, participating in the Green Bank conference where the modern SETI (Search for Extraterrestrial Intelligence) movement was born, and taking a position at Harvard. His 1966 translation/rewriting of a book by I. S. Shklovskii, Intelligent Life in the Universe, established him as a first-rate popularizer of science. That status didn—t win him friends in academia; in 1968 he was denied tenure at Harvard and moved to Cornell, where he became one of the stars of the faculty. From Ithaca, N.Y., he sallied forth to the Jet Propulsion Laboratory in Pasadena, to SETI conferences, and to Hollywood, to film Cosmos, the TV series that made him a household name. He was a fixture with NASA, contributing ideas to several major space missions—including the placing of a recording on the Pioneer spacecraft featuring samples of Earth’s music. He was also a key figure in the “nuclear winter” controversy, arguing that the long-term effects of nuclear war could exterminate humanity. His incredibly active career left behind 25 books and approximately 300 scientific papers. Poundstone (Prisoner’s Dilemma, 1992, etc.) doesn—t whitewash Sagan’s personal flaws but leaves the reader with added appreciation of just how rich his legacy was—and what a loss his early death was to us. A readable and comprehensive life of a fascinating subject.