Book excerpt: The best-selling author of Stiff and Bonk trains her considerable wit and curiosity on the human soul. "What happens when we die? Does the light just go out and that's that—the million-year nap? Or will some part of my personality, my me-ness persist? What will that feel like? What will I do all day? Is there a place to plug in my lap-top?" In an attempt to find out, Mary Roach brings her tireless curiosity to bear on an array of contemporary and historical soul-searchers: scientists, schemers, engineers, mediums, all trying to prove (or disprove) that life goes on after we die.