Having mined the depths of the bizarre with great success in "Stiff: The Curious Life of Human Cadavers," Mary Roach once again concentrates on an offbeat mix of science, pop culture and travel. "Spook" is an irreverent, yet thorough, exploration of the science of the afterlife. It tackles psychics, mediums, ghost detectors, NASA, and a host of other characters who are only concerned with what lies beyond. Unabridged.