The rather leisurely plot follows Ranjit, the son of a Hindu priest, from his days as a lackadaisical student in the Sri Lankan capital of Colombo, where he finds academic motivation only in his math and astronomy classes. Ranjit's first romantic love is his best friend, Gamini Bandara, and when that boy leaves Sri Lanka for London, Ranjit eventually takes a serious interest in Myra de Soyza, a brilliant young woman studying artificial intelligence.

Unbeknownst to Ranjit, or for that matter to anyone else on our planet, an armada of extraterrestrial assassins is on its way to exterminate humankind. Alerted by the explosions of the first atomic bombs, the almost-omnipotent Grand Galactics have decided that humans threaten their plans for the universe and must be wiped out as soon as possible. The Galactics' motivations are murky, but one of their main concerns boils down to: "Protect the harmless. Quarantine the dangerous. Destroy the malevolent - after storing a backup in a secure location.

"The Last Theorem" contains elements that will be familiar to fans of either co-author. In "Man Plus" and its sequel, Pohl explored the interface between man and machine, and that theme plays a key role in this novel's denouement. As in Clarke's "The Fountains of Paradise," a space elevator, a mechanical method of moving objects into space, plays an important role. And both authors have specialized in creating aliens with inscrutable motives. Witness Clarke's "2001: A Space Odyssey" and its sequels, and Pohl's books about the Heechee, beginning with "Gateway.