BOOK REVIEW : ‘After Moondog’: A Wry, Worldly Novel : AFTER MOONDOG <i> by Jane Shapiro</i> ; Harcourt Brace Jovanovich $22.95; 269 pages

All through the 1960s, Moondog stood on the corner of 54th Street and Avenue of the Americas in his battered silver Viking helmet, wearing an assortment of blankets and assailing passers-by with a torrent of words.

Although there were other street people even then, none was as theatrical, none as exuberant. The characters in this novel, like everyone else in that age of innocence, assumed that Moondog stood there because he enjoyed the ambiance. Homeless was still only an adjective, not a noun. New Yorkers seemed oddly proud of him; a shining symbol of the city’s diversity. One day he simply vanished, leaving the streets to the lost, the mad and the menacing.

Joanne Green, the narrator of this wry and worldly novel, met her husband on Moondog’s corner. William was a law student with a passionate interest in jazz; Joanne was wondering what she’d do after graduation. All that was quickly settled. They married; William became a lawyer, and the Greens moved to the suburbs and had two children.

Their story is a social history of the succeeding two decades, told in separate chapters that lock together in a tight, mortarless bond. Spare and terse, “After Moondog” speaks so directly to general experience that it seems almost interactive. Reading the story of Joanne and William, we supply the connections and the details, participating in spite of ourselves.

The opening chapter is followed by a fast forward to a time when the Greens’ daughter, Nora, is 6; her brother, Zack, 7. The Vietnam War is finally over, but people aren’t quite as relieved as they expected to be.

When major problems disappear, minor ones loom large. Joanne and William have become estranged “while we were looking the other way.” Joanne is teaching remedial English at a school for juvenile delinquents, an occupation that offers a wonderful opportunity for her to display both wit and compassion. Once in a while, they still amuse each other doing impersonations, but these occasions are separated by increasingly long stretches of tension. No explanation is necessary when Joanne acquires a lover.

Aside from his interest in dance, Dan is every bit as tedious as William, but in a different, more endearing way. He’s a international economist, specializing in the theory of rational expectations, which Joanne interprets to mean “if you decide to do it, it’s already done,” a perfect precis of their affair. During this period, William is also having a fling, and the rift widens.

A divorce is embarked upon, divorce being the central metaphor of our time, perhaps even the central experience of our century. While no more or less excruciating than most, this one is more fascinating to read about, because the author has kept the acrimony to a minimum while emphasizing the ambivalence. The children, Nora and Zack, have grown into delightfully sage and winsome adolescents, offering some genuinely astonishing glimpses of teen culture in a New Jersey university town during the early 1980s. We’re reintroduced to Joanne’s mother and William’s father, who supply a generous measure of both pathos and humor to what otherwise might be a somewhat hermetic story line.

And that is essentially where “After Moondog” excels. The focus is kept firmly upon the particular, against an increasingly encroaching background of the general. Although Jane Shapiro’s narrator modestly describes the book as “a story about us when we were young, more plausible than most,” the “us” is an entire generation; maybe two, observed by a woman who manages to keep the subjective and objective in exquisite balance.