Set in a spare, smoke-and-mirror-filled world of secret Web sites, Goth bands, Satanism, pornography, and outsider art, "Period" is a literary disappearing act as mysterious as it is logical. The culmination of Cooper's explorations into sex and death, youth culture, and the search for the ineffable object of desire, "Period" is a breathtaking, mesmerizing final statement to the five-book cycle it completes.