If there’s anyone qualified to write a book about the 1906 San Francisco earthquake and fires, it’s Simon Winchester. A geologist whose best-sellers include Krakatoa and The Professor and the Madman, Winchester has a talent for (a) writing about rocks and (b) prodigious research. Which is why A Crack in the Edge of the World is such a letdown. Arriving after Hurricane Katrina — which has arguably replaced the quake as America’s worst natural disaster ever — Crack disappoints with its relative lack of human drama. Winchester spends almost the entire first half of the book (nearly 200 pages) discussing plate tectonics, the history and landscape of the American West, and the creation of the San Andreas Fault. He obviously considers the earth to be as deserving of character development as any single person, but the people here barely register on his Richter scale.