If you are interested in this issue, I highly recommend the book. This book is extremely thorough, so thorough it could be used as a textbook on an astrobiology class. It was written in the sixties so yes its out of date here and there, but much of the information is surprisingly current. You also get a great early taste of Sagan's writing style.
The single best scientific book on intelligent life in the universe, December 6, 2005
Reviewer: B. Marshall (Washington, DC)
I used this book as an undergrad in a 400 level Astronomy class. At the time, the book was a real challenge for me in that I wanted to understand the mathematical and physical foundations of intelligent life. By the end of the course, and the book, I was, and have remained, absolutely convinced that intelligent life is plentiful in the universe, at least as can be "proved" mathematically using our physical laws. I was also convinced that human type life is in fact highly unlikely to be duplicated elsewhere in the universe. Finally, it is likely that many of this other intelligent life is perhaps vastly superior to our own. No, I'm not a nut, and I'm not a scientist, but I am convinced, even in the absence of physical evidence. Read this book, you'll make your own mind up. One warning, this is not "light reading". It is a college level textbook, that if you stay with it, will reward you in the end. What a shame we have lost such a great mind as Carl Sagan. To date, no one has stepped up to replace him.
Carl S. reviewed Intelligent Life in the Universe on
This is a remarkably thorough updating and restatement of Shklovkii's "Universe, Life, Mind" w/ much new material added by Carl Sagan. Though published over 40 years ago it presents a much broader and more balanced exposition of cosmology than modern-day popular science accounts with their absurd pretence of explaining everything through garbled and mysterious references to pseudo scientific concepts such as "dark matter" and "dark energy", and the quixotic quest for a Theory of Everything.