From the back cover:

Doomsday began with a massive California earthquake. Everybody assumed it was the Big One that geophysicists had been predicting for years. But odd pieces of evidence came together in the hands of a brilliant group of scientists that pointed to a disaster far more catastrophic: a tiny -- but very real -- black hole.

Now the singularity was looping its way around -- and through -- the Earth, and slowly but certainly the planet was being consumed. But how do you stop something that is smaller than an atom, heavier than a mountain, and swallows everything that touches it?