This book has two hypotheses:
1. Evolution is convergent (it tends to converge on specific traits rather than wander through all possibilities like a headless chicken) to the extent that human-like intelligence has not evolved by random chance. This is a fascinating idea on its own and therefore explored at length in this book, but it also has implications for the idea to find extraterrestrial intelligence.
2. The chemical, physical and astronomical constellations to create life on earth are unlikely in such a manner that we indeed might be alone in the universe.

To explore these premises, Simon Conway Morris goes through a wide variety of scientific topics: The chemicals that might lead to DNA and life, the computational elegance of the DNA code, astronomical considerations for life on planets and lots of paleoanthropological and biological examples from evolution that are convergent: camera and compound eyes, eusocial and/or agricultural life forms like certain ants or moles, dolphin intelligence     and many more.

By reading this sentences, I get the feeling that I would not pick it up because it sounds like some heap of backdoor-arguments to darwinian evolution. It's not. This is no basic attack on Darwin, but rather scientific. Somewhere it deals with the topic of fundamental darwinism, though.

There's a lot in this book. I recommend it. The only thing I might object is that for the sake of getting the scientific argument founded, there are some examples of convergence too much, but it's not too bad and apparently, he rather added too much than too little.