What was the title of Carl Sagan's final book, published posthumously?

Carl Sagan’s final book was Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium. It was published posthumously in 1997, after Sagan died in December 1996.

The book is a collection of essays on subjects including global warming, population growth, extraterrestrial life, morality, and the abortion debate. Its final chapter describes Sagan’s struggle with myelodysplasia, the illness that preceded his death. His wife and longtime collaborator, Ann Druyan, wrote the epilogue after his death.

The title also explains a famous Sagan mix-up. Many people remember “billions and billions” as one of his catchphrases, but the phrase was popularized largely through Johnny Carson’s parody of Sagan on The Tonight Show. Sagan did not actually use it as a signature spoken phrase, although he adopted it as the title of his last book. The book followed The Demon-Haunted World and preceded the posthumously assembled The Varieties of Scientific Experience.