Rare Earth: Why Complex Life Is Uncommon in the Universe Peter D. Ward, Donald Brownlee (2004)

This book marshals data from geology, astronomy, and biology to put forth a radical hypothesis: while primitive organisms such as microbes are very likely abundant across the galaxies, advanced life, depending as it does on a myriad of special circumstances, is altogether another story, In a thought-provoking departure from the widely held view that there must be countless civilizations of intelligent beings out there, Ward and Brownlee suggest that multicellular life-forms, let alone life-forms with whom we'd be able to communicate, must be exceedingly rare.