As John Dunne sees it, a writer's life has two states: writing and having written. Right now Dunne is in the latter one and relieved. He finished his book, "The Red, White and Blue," on April 6, 1986, at 2:06 in the afternoon, he says with his passion for factual precision. "And that was a Sunday, I believe," he adds.

Now he is waiting for March publication. In the interregnum, he is at loose ends, feeling "awful," writing about writing for Esquire magazine to keep going; he calls publication "the afterbirth"--an anticlimactic emptying necessary before gestation of another book can begin.

Down the hall in her white shoe box of a space, Joan Didion's fingers tick over the keys of her IBM typewriter, as hour after hour she heads toward a March deadline. She is on a regime of 20 pages of rewrites a day for "Miami," a nonfiction book about the city's Cuban community, scheduled for appearance in September. She is working eight hours a day, seven days a week. To relax in the afternoon, she drinks lemon grass tea, brewed from fresh stalks from her vegetable garden. When she breaks off at 7 p.m., she is tired and stiff.

One of the country's most celebrated literary sets, Dunne and Didion have been married for 23 years, and during that time have shared the exhilaration and frustrations of their metier in a rare, harmonious collaboration, with only an errant slip toward dissolution.

For as many years, Dunne and Didion have lived in Los Angeles. As novelists, screenwriters and journalists, they have long mined the contemporary issues and cliches that inform the East Coast's standard text on Southern California. In a prose style that is eloquently chic and bleak, Didion has described the alienation and disquiet that is particular to Los Angeles; Dunne's narratives, as unsparing as the local subtropical sun, have transfixed the netherworlds of Los Angeles crime, Hollywood and Las Vegas.

Yet in more recent years--in "Democracy," "El Salvador" and now "Miami"--Didion has expanded her horizons to examine the sociopolitical impact of United States relations with less powerful peoples. In his new novel, Dunne also branches out, drawing an ambitious panorama of America in the '60s and the decade's aftermath.

As their literary interests move afield, Dunne and Didion are considering a change in residence--pulling up stakes in Brentwood and focusing their lives from their New York beachhead, closer to the material of future work. "I may be wrong," Dunne says, "but I think I've written everything I have to say about Los Angeles. I feel tapped out about it."

At 54 and 52 years old, respectively, Dunne and Didion say they are also seeking a quieter life than the one they are known for as bicoastal celebrity writers.

But the change is more a mutation than a break in their lives, which have always been a hybrid of personae and places.

On a springlike winter's day, there is no indication of a writer's anguish in Dunne's demeanor. He welcomes a visitor into his donnish, book-lined office with the bulldog gregariousness of a tavern keeper. He is a large, robust man with a florid face and a hearty laugh, who thinks of himself as "gutter Irish."

A tale is forever tickling the tip of his tongue. Hardly have greetings been exchanged than he's telling how artist Robert Graham gave them the black bouvier des Flandres named Casey, who trots at his heels. Graham also gave a police dog to Dunne's neighbor Norman Lear; the first bouvier he and Didion saw belonged to the New Yorker's Paris correspondent, Jane Kramer.

This is unadulterated Dunne--the kind of garrulous, urbane rush of names and places that overlays his books. Yet, lightly laced through the banter are traces of a doubting childhood stutter and an unwinking eye that fixes life's darker pockets and the secret sins of its inhabitants.

Charting the world of Irish Catholic Americans "playing life in the dark keys," Dunne writes in a blackly comic Celtic voice magnetized to misfortune.

Yet, in the here and now of palm trees and limousines, he and Didion appear to lead exemplarily happy, leisured lives.

On this afternoon, Dunne wears khaki pants and a shirt the color of a bruise. Hanging over an office chair is a vintage tweed jacket, custom-tailored at Tartaglia in Beverly Hills.

Small, waiflike and initially shy--though "tough as nails," Dunne affirms--Didion was brought up in Sacramento, a fifth-generation Californian, an Episcopalian, a Berkeley graduate. She gardens, "a new fashion" she says, and keeps Penelope Hobhouse's "Color in Your Garden" on the coffee table; she is also well-known for her cooking, an activity that "wipes everything clean," she says.

She whisks stray auburn bangs from her forehead as she pads across the wide-boarded floor of the den, serving tea in a Haviland china service decorated with birds and flowers. She wears her writer's "work clothes"--tennis shoes, sweat pants and a baggy sweater. On a chain around her neck hang her wedding ring and the baby ring of their adopted daughter, Quintana Roo.

In the rustically homey rooms around her, "shards of memory," of the kind that would torture Dunne-Didion protagonists, comfortably mark the course of their marriage: maps of where they've been (even Quintana is place-specific, named for the Yucatan state), photos of people they know and a filing room the size of a small-town newspaper morgue, packed with letters and journalists' notes. The white two-story house is so traditionally Eastern that when Didion found it she exclaimed to Dunne, "Your mother will love it!"

But Dunne and Didion are characteristically unsentimental about the house where they have lived for the last eight years. "Home is probably overrated anyway," Didion says in her soft, almost inaudible voice that so unexpectedly shatters conventional thought. "I could be in South Africa here."