ON THE ROAD by Jack Kerouac (Penguin: $6.95). When "On the Road" finally appeared in 1957, Jack Kerouac's most productive period as a writer was over, and the "beat" movement that his novel helped to define and epitomize already was waning. The frenetic travelogue of a loosely knit group of buddies crisscrossing the continent, boozing, whoring and "digging the scene," "On the Road" catalogues the postwar search for meaning in live-for-the-moment intensity, absolute honesty and a voyeuristic fascination with ethnic subcultures. (" . . . I walked with every muscle aching among the lights of 27th and Welton in the Denver colored section, wishing I were a Negro, feeling that the best the white world had offered was not enough ecstasy for me, not enough life, joy, kicks, darkness, music, not enough night. . . .") Despite its enormous influence, "On the Road" hasn't aged well. Dean Moriarty and the other characters don't seem outrageously free or possessed, but self-centered, irresponsible and cruel as they leave a trail of wrecked cars, bad debts and broken hearts for others to deal with. Kerouac's frantic amphetamine rushes of verbiage get to be nerve-wracking after the first few dozen pages: Truman Capote had a point when he said of the book, "That's not writing, it's typewriting."