When the aliens arrive on earth, their first action is to march into one of the world's leading museums and demand "take me to your paleontologist!" They're not interested in politics, not interested in conquering the world or curing human disease, they just want to study our fossil record. And so the alien Hollus meets Tom Jericho, director of paleontology at the Royal Ontario Museum, and confirmed atheist. And Tom is rather surprised and disturbed to discover that the aliens are so interested in our fossil record because they believe they've found evidence of god.

The story continues on several levels - Tom's personal life and struggles, the debate between Hollus and Tom over whether the evidence the aliens have put forth does in fact constitute proof of an intelligent force influencing the universe, and also the reaction of more fundamentalist political and religious groups to the alien's arrival (and announcement of their belief in a god).

I haven't read up on Sawyer's background but the book reads like an atheist and scientist author who has decided to play devil's advocate and turn the stereotypical narrative upside down and see what happens. He constructs a quite realistic scenario in which an all-powerful creator's influence CAN be scientifically justified, and then takes it to a far extreme to see what happens. The book is quite cerebral in parts, as it does get fairly heavily into the discussion of science, philosophy, and religion, but I found it a very interesting and thought-provoking thought experiment, as well as ultimately a touching story. If you're not interested in a little mental exercise and just want a story you can take at face value though, this is probably not the book for you.