Louis Auchincloss is happiest when he has some literary work in progress. "You shouldn't say that," he says. "You should say that each word is agony, but in my case it's just not true. I'm unhappy when I'm not writing."

In order to keep himself content over the past 30 years, Auchincloss, now 56, has produced 24 books—novels, essays, stories and biographies of Edith Wharton and Cardinal Richelieu. He wrote 18 of them since his marriage at almost 40 to Adèle Lawrence, a Vanderbilt descendant.

A highly disciplined craftsman, he can write while listening to music or pause to jot down an insistent phrase as he is answering a son's question. Appropriately, this literary work is done on long yellow legal pads, for Louis Auchincloss lives another life as a senior partner in the eminent New York law firm of Hawkins, Delafield & Wood.

It so happens that his latest, best-selling novel, The Partners, chronicles the corporate life of such a Wall Street law firm. While he is often considered a novelist of manners and mores, much of Auchincloss' concern as man and writer is with the old-fashioned virtues of honor and probity. Auchincloss says, "The great men of the law when I began had tremendous personal integrity. They were more independent of their clients than we are."

The Partners points up the ethical evolution in the practice of law over 50 years as seen through the eyes of Beekman ("Beeky") Ehninger, the partner who holds the firm (and the book) together. This is how Judge Howland, the firm's founder, puts matters to "Beeky" in the novel: "What the evil temptation usually boils down to is that you are asked to misrepresent a fact. A good way to avoid it is to avoid too many professional intimacies. Most of the easy camaraderie in American business life is intentionally designed to create intimacies that can be taken advantage of."

Born into an old and distinguished New York family, Auchincloss was not a rousing success as a youth. A handsome, unathletic misfit at Groton, he became a grind in order to win some peer approval. At Yale he plunged into the cultural past and became a Francophile, concentrating on that country's 17th-century literature.

His mother, a society grande dame, saw him then as "a dilettante" unlikely to become one of the substantial professional men who peopled her world, he admits in a just-published and revealing short memoir, A Writer's Capital. Young Auchincloss demurred, and his creative outpouring followed what he now recalls as his "angry resentment of her refusal to see that I might be something altogether different: a great writer, a great actor, a great professor, a great individualist, a great something."

To parental dismay, he wrote a novel. When it was rejected by Scribner's, he abandoned Yale in his senior year to enter law school in Charlottesville, Va., where he put fiction behind him. Four years of wartime naval duty followed. In 1946 he joined Sullivan & Cromwell, the large and prestigious Wall Street law firm, as a law clerk. He ventured back also to writing. Like most young lawyers, Auchincloss worked such grueling hours that a few years later he made the hard decision to resign and write full-time. After two years, missing the discipline that the law exacts, he joined his present firm. Today he is a respected authority on trusts and estates by day and a writer by night and weekends. He is, too, the paterfamilias his mother wanted him to be: devoted husband and father of three sons (15, 13 and 10). He is also an enthusiastic book collector and the president of the Museum of the City of New York.

Although by worldly standards Louis Auchincloss is an outstanding success, he would not advise others to live his dichotomous life. "I am—or would have been—least respected by those I most respect," he says, a little ruefully. "Henry James would never have understood my passion for the law, and Judge Learned Hand could never see why I wanted to write fiction."