MEXICO BAY is a praiseworthy novel, but first a

few words of praise for its author. Paul Horgan, who is a year shy of his 80th birthday, is something of a national treasure. In a half-century of writing he has produced 42 books, of which Mexico Bay is the 26th work of fiction. Several of these books have won a respectable degree of popular success, but he has never achieved it at the price of lowered standards; in everything he writes he is at the least a solid craftsman, at the most a vivid stylist. Over the years he has received an array of honorary degrees and appointments, teaching positions at several prestigious colleges--and the high respect of his fellow writers.

Though Horgan was born in the East, he has been primarily a novelist and historian of the West. His is not the West of Zane Grey and Louis L'Amour, but that of Willa Cather: a West of pioneers and settlers, of priests and ranchers, of ordinary people set down in an extraordinary landscape. As characteristic as any of his works is Lamy of Sante Fe, a biography of the priest whose life was the basis for Cather's novel, Death Comes for the Archbishop ; the life of Lamy, with its beguiling mixture of deep spirituality and frontier courage, seems to epitomize the characteristics that Horgan admires, in the desert setting with which he is most comfortable.

In Mexico Bay Horgan wanders a bit beyond his customary territory, taking in not merely the Southwest but also the nation's capital. The book is set, in large part, in the early days of America's entry into World War II, and it is my guess that in tone if not in actual incident it is heavily autobiographical; it has an air that is at once nostalgic and elegiac, as though Horgan were harking back to a lost time that has particular and profound meaning for him. In the best sense of the term it is an "old man's book," one that looks to the past with affection, pride and clarity.

It is primarily the story of two people. Howard Debler is a young historian who is researching a study of the Mexican War, with the hope of writing a book that will capture the human and intimate aspects of combat. Diana Macdonald is the daughter of a prominent newspaper publisher and the former wife of an equally prominent playwright, Jack Wentworth; now she is living on the Texas Gulf Coast with her lover, a talented and charismatic artist named Ben Ives.

Howard and Diana knew each other slightly before the war, when he spent several days examining her father's collection of Mexican War documents. Now, after the war, they meet again on the coast, a place where "elements were aged, and had proved themselves unchanging in the scale of human measurement--sea, sky, dunes, the sound of waves on the chordic wind saying peace and forever. " This new encounter triggers extensive flashbacks to the early years of marriage to the suave and self-important Wentworth, a marriage that evidently was one of mutual convenience and no passion. Soon after Pearl Harbor, in that hour of "the mammoth heavings of a new national spirit stirring alive," Wentworth maneuvered a place in the wartime government and headed for Washington:

"An ambitious and privileged throng of the population converged on Washington. For them, Washington became, for whatever motive, 'the thing to do.' Jack Wentworth, with his sense of public style, was one of the first to enact the imperative. He awaited the arrival of his wife Diana impatiently. He was already too busy to give thought to domestic matters; and Diana was needed to set up the suitable establishment in Georgetown."

That she did; the Wentworths entertained official Washington and Jack acquired a reputation as a witty and gracious host. But when he attempted to arrange a friendship--an affair?--between Diana and Ben Ives, his tactics backfired; they ran off together, and he was left with a considerable embarrassment. Now, in the present, all are reaping the consequences of their actions. Diana, who has moved to the center of the novel, is caught up in a grand passion that eventually proves excessive; the tempestuous Ben commits a dreadful folly, and she is left to put the pieces of her life back together, to make "a choice between nothing and possibility."

The story of these people and their tangled lives is interesting and Horgan tells it with characteristic skill. But the real strength of Mexico Bay is its evocation of wartime Washington: the excitement of uniting behind a "just war," the fierce competition for social standing, the hectic and often mysterious comings and goings, the tension and the giddiness. Only in some of the novels of John P. Marquand--notably So Little Time and B.F.'s Daughter --is that vibrant time and place so keenly depicted. Horgan has a sharp sense of the city, as in this memory of Union Station at the height of its glory:

"They went to the long restaurant which was in general darkness but for spotlights which shone separately upon little groups of people at spaced tables. Smoke from cigarettes made the cones of light pale blue. A face caught in that illumination was modeled into a mask and Ben half-closed his eyes to memorize it. There was a common grace over everything in that vivid light which made private and intimate that which everyone could see. Beyond the big room the trundel of trains, the glisten of throngs on the waiting platforms, the roll of carts, gave a pulse of life which could be felt in the bones. The place was charged with emotion, the sum of the comings and goings that happened there."

Paul Horgan is not a flashy writer. His prose is quiet and modest, yet insistent; its rhythms move the reader through the story more forcibly than one realizes--past, in fact, a few excessive, but forgivably so, twists and turns of plot. Mexico Bay is not one of the larger works in his imposing canon, but it is unfailingly interesting and arresting.y