New York magazine's witty, cheeky book critic Walter Kirn rides high in his exhilarating second novel, and so does his protagonist, Minnesota teen dweeb Justin Cobb. Justin's hippie dentist may have hypnotized him out of his socially perilous thumbsucking habit, but he can't suppress the boy's "oral gift." Justin's mouth just won't quit: beer, decongestants, nitrous oxide, cough syrup, Midol, and Ritalin go in, and out spritzes hilarious commentary on his eccentric yet authentic life and times. Our hero's mood larks and plunges erratically, but Kirn's prose is alert, artful, under control. The debate coach's skin is "the neutral hue of turkey meat." One of Justin's realistically inconclusive crushes is a redhead "with freckles the color of new pennies." Her dad is a Limbaughesque columnist who calls welfare recipients "food tramps." Meanwhile, Justin's dad, Mike, is "the Führer of fly-fishing," an ex-gridiron hero obsessed with deer hunting (and eating). He's also prone to spouting his vile old coach's preposterous apothegms ("Until you're broken, you don't know what you're made of"). Mike is funny and poignant--a tricky note to hit. Like a mucked-up modern Huck Finn plying his own stream of consciousness, Justin drifts into weird scenes: a job at a gas station fated for torching, a visit by his mad Winnebago vagabond grandparents, a kidnapping caper to rescue a pothead infant from sinister hick parents, Grit and Munch. Chapter 4, about a Chippewa City debate mee