Did you know that in dream imagery printed letters almost always mutate and clock faces quiver? Or that studies show that the anatomy of dreaming is almost identical to schizophrenic psychosis -- the difference being that dreamers hallucinate images, schizophrenics sounds? I didn't. And that made ''The Mind at Night'' a damned compelling read. Award-winning science writer Rock packs a lot into a slim, potent 200 pages: from cocktail-ready factoids to clean, crisp explanations of brain chemistry. It lingers like a sublime night vision.