THE CITY AND THE HOUSE By Natalia Ginzburg Translated from the Italian By Dick Davis Seaver Books. 219 pp. $16.95

THERE ARE some literary virtuosi who can leap across genres as stylishly as Superman hurdles tall buildings. Among this small group of protean talents, the Italian novelist Natalia Ginzburg must surely have a special place. In addition to being a current member of the Italian parliament, Ginzburg is a well-regarded European poet, critic, essayist, short story writer, and prize-winning dramatist and novelist.

It is probably the cool, understated novelist who is best known to American readers. In such previous works as A Light for Fools, Family Savings, and No Way, she has served us violent death and bereavement as calmly as the morning toast. The City and the House, her latest novel, is no exception.

Like No Way, her new book is also an intriguing collection of letters. These letters tell the story of two friends and former lovers, Giuseppe and Lucrezia, and the disintegration of their families. Bored with their lives and depressed to one day discover themselves middle-aged, each makes a fateful decision. Giuseppe recklessly sells his apartment in Rome, where he can no longer breathe, and hurls himself into America in hope of a sea change. With no less melodrama, the married Lucrezia takes a new lover. "My adultery," she writes joyously to Giuseppe, "is of the kind that scatters blood all over the place."

The experiences of these two, though occurring on different continents, have an eerie similarity. Perhaps it's because they are so much alike in their childish impulsiveness and need to be protected. One of their friends explains Giuseppe's flight to America as a futile attempt "to hide himself away under his brother's wings." But his brother, Ferruccio, a professor of biology at Princeton, marries just prior to Giuseppe's arrival and the visitor wonders if he's made a mistake in coming. Reassuring him, Ferruccio insists that "The three of us -- you, Anne Marie, and I -- shall live very well together. Three is, as you know, a perfect number."

Three, however, proves to be anything but perfect in Ginzburg's fiction. Shattering the triangle that her marriage has become, Lucrezia abandons her husband and their big, old, comfortable house in the country. "The strange thing is that everything is breaking up here," she writes to America, "the whole house is falling to pieces." Dragging her children after her "like luggage," she pursues her handsome lover, Ignazio Fegiz, to Rome. There, ironically, she discovers that he has a long-standing, intimate relationship with another woman. Though all nose and hair, this woman is nevertheless indispensable to him and, much to Lucrezia's dismay, together they form yet another "perfect" three.

Unquestionably the most striking threesome in the novel consists of Giuseppe's son -- the drug-taking homosexual moviemaker, Alberico -- his lover Salvatore, and their pregnant unwed roommate, Nadia. "Deviance" is Alberico's defiant title for his movie-in-progress and, with a witty inevitability, the film is a hit. For a time, the friends actually seem to achieve a successful triangular relationship and, when Nadia's baby is born, Alberico adopts her as his own. But society does not smile on odd numbers, and the brutal, perhaps drug-related murder of the three comes with devastating force.

The epistolary novel has survived over the years from Richardson's Clarissa to Saul Bellow's Herzog and Alice Walker's The Color Purple because of the instant intimacy it provides while trading on the illicit appeal of reading other folks' mail. What is said in the privacy of a letter can be cruelly candid. Giuseppe writes mockingly of his son in his black clothes who "looks like a hearse," and the spiteful Lucrezia, miffed at her daughter, confides to the post, "I think she's grown ugly."

An additional attraction that the epistolary form holds for novelists is that events do not require long narrative preparation to be credible. Since they are being recounted after the fact, they can leap out of their envelopes with shocking abruptness. If the marriage of Ferruccio on the eve of Giuseppe's arrival comes as a surprise, the announcement shortly thereafter of his sudden death takes one's breath away. Instead of presenting dramatic scenes, Ginzburg constructs a pattern of reported births and deaths, and the cumulative impact of these revelations creates its own dramatic intensity.

One of the problems in using letters to tell a story is that of exposition, and it is a difficulty not entirely overcome here. In order to inform the reader about Giuseppe's cousin or Lucrezia's mother, the author employs such awkward and unconvincing formulas as "You know this because I've told you about it" or "I think you know her" and then proceeds to describe the person as if she were a stranger.

A further irritant -- though this is in no way the author's responsibility -- is the translation, which is pocked with such Britishisms as "bedsit" and "windcheater." It's too bad that an American publisher can't provide an American translation of the work of this important Italian novelist.

Surrounded by the din of ringing telephones, Virginia Woolf once observed, "Letters aren't written nowadays" and proceeded to write hundreds of them. In The City and the House, Natalia Ginzburg's fictive correspondence is also impressive; her esthetic achievement, however, is of a more subtle and complex order. Not only has she given us a collection of letters, but a novel and a world as well. ::

Gerald Jay Goldberg's most recent novel is "Heart Payments." His forthcoming novel is "Dancing by Starlite."