Wizard and Glass, the fourth episode in King's white-hot Dark Tower series, is a sci-fi/fantasy novel that contains a post-apocalyptic Western love story twice as long. It begins with the series' star, world-weary Roland, and his world-hopping posse (an ex-junkie, a child, a plucky woman in a wheelchair, and a talking dog-like pet named Oy the Bumbler) trapped aboard a runaway train. The train is a psychotic multiple personality that intends to commit suicide with them at 800 m.p.h.--unless Roland and pals can outwit it in a riddling contest. It's a great race, for the mind and pulse. Films should be this good. Then comes a 567- page flashback about Roland at age 14. It's a well-marbled but meaty tale. Roland and two teenage friends must rescue his first love from the dirty old drooling mayor of a post-apocalyptic cowboy town, thwart a civil war by blowing up oil tanks, and seize an all-seeing crystal ball from Rhea, a vampire witch. The love scenes are startlingly prominent and earthier than most romance novels (they kiss until blood trickles from her lip). After an epic battle ending in a box canyon to end all box canyons, we're back with grizzled, grown-up Roland and the train-wreck survivors in a parallel world: Kansas in 1986, after a plague. The finale is a weird fantasy takeoff on The Wizard of Oz Some readers will feel that the latest novel in King's most ambitious series has too many pages--almost 800--but few will deny it's a page-turner.