In the final book of his astonishing career, Carl Sagan brilliantly examines the burning questions of our lives, our world, and the universe around us. These luminous, entertaining essays travel both the vastness of the cosmos and the intimacy of the human mind, posing such fascinating questions as how did the universe originate and how will it end, and how can we meld science and compassion to meet the challenges of the coming century? Here, too, is a rare, private glimpse of Sagan's thoughts about love, death, and God as he struggled with fatal disease. Ever forward-looking and vibrant with the sparkle of his unquenchable curiosity, Billions & Billions is a testament to one of the great scientific minds of our day.

In a book completed less than two months before his death, Sagan (The Demon-Haunted World, etc.) compels his readers to look at life. Although many of the essays here have appeared previously, they gain power through juxtaposition and new commentary. They portray humankind as a favored species on a fragile world, facing the profound impact that 20th-century technology will have on its future. Six essays on "The Power of Beauty of Quantification" celebrate science and the insights it gives us into the cosmos, our planet and our species. Seven more, exploring the question "What are Conservatives Conserving?," discuss the political and economic factors that have led to quite different international responses to two environmental threats: the "ozone hole" and global warming. These pieces culminate with a joint appeal from scientific and religious leaders committed to saving the planet. The interplay among scientific, religious and political thought continues in the closing set of six essays, "Where Hearts and Minds Collide." Here, Sagan prompts readers to look beyond their own lives and to the preservation of our species and our world. As the author's widow, Ann Druyan, writes in her epilogue, "For Carl, what mattered most was what was true, not merely what would make us feel better. Even at [the moment of death] when anyone would be forgiven from turning away from the reality of the situation, Carl was unflinching." So should we be, says this book; the life of our species on our delicately balanced planet depends on it.