In the early morning hours of April 18, 1906, San Francisco was overcome by the violent shocks of an enormous earthquake, registering 8.25 on the Richter scale. The tremors and rumbling, affecting a swathe of California more than 200 miles long, triggered a vast firestorm in the city, effectively destroying the gold rush capital that had stood there for half a century. Simon Winchester brings his inimitable storytelling abilities to this extraordinary event, exploring not only what happened in northern California nearly 100 years ago, but what we have learned since then about the geological underpinnings that caused the earthquake in the first place.