A Baedeker to the sprawling, brawling world of dinosaur research. Lessem, a science journalist who has founded the Dinosaur Foundation to promote the study of every kid's favorite beasties, delivers a comprehensive survey that rarely takes sides. That's no mean feat, for dinosaur studies are in an uproar. Depending on who's talking--or shouting--dinosaurs were either swift or slow, smart or stupid, hot- or cold-blooded, solitary or communal. Lessem reports it all, which gives his book a loose-jointed feel (like one of those fossil skeletons that barely hangs together) but nonetheless catches the heady energy running through the field these days. The scope is worldwide. In China, paleontologists make spectacular finds in a repressive academic environment. In Nova Scotia, Paul Olsen studies an ``event''--an asteroid-Earth collision--that may have aided the rise of the dinosaurs. In Argentina, Paul Serino hunts for the first dinosaur and finds a possible candidate. Everywhere looms the neon-bright, pony-tailed, cowboy-hatted presence of Robert Bakker, the media hotshot who popularized the idea that dinosaurs were hotblooded beasts that eventually evolved into our neighborhood songbirds. Lessem, while ever the diplomat, seems more partial to soft-spoken Jack Horner, an expert on fossil eggs and nests who sees duckbilled dinosaurs as paragons of mother love. Enjoyable if unfocused, offering ample evidence that paleontological research, which once seemed dry as dust and cold as clay, is now a red-hot bone of contention.