THE ESTATE of Kilneagh, like the garden of the Finzi-Continis, is a seemingly inviolable oasis of beauty and serenity in a world where the threat of madness and destruction grows ever more ominous. To 8-year-old Willie Quinton, son of its owners, "a straw-haired boy with the family's blue eyes and a face that caused strangers to enquire if I were delicate," it is heaven on earth: "Aunt Fitzeustace cuts the grass, old Hannah arrives from the village to scrub the floors and do the washing, Tim Paddy leaves spinach for Mrs. Flynn at the back door, O'Neill is hunched among his high delphiniums. The millyard bakes in the afternoon sun, my father walks the length of the avenue, his labradors slouching with him."I am old, but let me drink," my mother prompts in the scarlet drawing-room and adds in the silence that follows: "Bring me spices, bring me wine.""

It is heaven, but it is also Ireland, in the summer of 1918. The war in Europe has ended, a war in which Irish troops fought in defense of the hated English, and the "Troubles" are beginning; "everything was unsettled and on edge." Eamon De Valera is in Lincoln Gaol, but the revolutionary fight for home rule that he led continues to be waged; it is a fight in which the Quinton family, though Protestant and with strong ties to England, is quietly but deeply engaged. All about are fear and danger:

"A force of British soldiers known as the Black and Tans because of the color of their uniform had been sent to Ireland to quell the spreading disobedience. By reputation they were ruthless men, brutalized during the German war, many of them said to have been released from goals in order to perform this task. The Irish gunmen who rampaged through the countryside had become, in turn, ruthless themselves. They gave no quarter and, knowing the lie of the land, were often more successful in the skirmishes that took place. There was a Black and Tan force at Fermoy, which brought this spasmodic but intense warfare close to us."

Thus it is that the horror comes to Kilneagh, just as it does to the garden of the Finzi-Continis, even though Willie's father refuses to permit revolutionary units to occupy his estate's grounds. A worker at Kilneagh's flour mill is discovered to be an informer in the pay of the Black and Tans. He is lynched: hanged, his tongue cut out. The killing horrifies and infuriates the Quintons -- it "was a terrible thing," his father tells Willie -- but they cannot escape its repercussions. A Black and Tan force attacks the estate by night, exacting a vengenance at once apallingly misdirected and wildly out of proportion to the original offense. For the few survivors, Willie and his mother among them, life can never be the same.

Against this heartbreaking backdrop of retribution, death and unceasing anguish, the Anglo-Irish writer William Trevor has written a story of courage and love. It is his ninth novel and, in the judgment of his American publisher of many years, the one that will at last earn him a following on this side of the Atlantic; certainly it is a judgment that deserves to be fulfilled, for Fools of Fortune is arresting, powerful and indelible -- yet at the same time as tender and wistful as an Irish lament.

After the terrible events of that summer night in 1918, Willie undergoes a series of less calamitous but almost equally traumatic events: a move away from Kilneagh to Cork, and to a school where an excessively solicitous teacher embarrasses him; matriculation in a rough boarding school, his father's alma mater, where he learns to flip butter patties onto the ceiling and drink stout; the dawning realization that his mother, "the victim among the three survivors of Kilneagh," has turned to alcohol for relief; and, worst of all, his mother's death, which leaves him stunted with guilt and grief even as he embarks on the mission of revenge that is his tribute to her.

In this grim life, Willie finds only one pleasure; his English cousin, Marianne, slightly younger than he, who comes to visit and with whom he falls passionately in love, as she does with him. On the night of his mother's funeral she comes to his room, where they make love. She becomes pregnant, and he disappears. But when it is time to have her child she returns to Kilneagh: "More than ever, Kilneagh was a fearsome place and yet there was nowhere else I wished to be. No matter how grim that half-ruined house was, no matter how much nobody there wanted me, it was where I belonged because [Willie] had belonged there also."

Not merely does Marianne go to Kilneagh because of her love for Willie; she also goes because, like the other Englishwomen of other generations who married into the Quinton family, she has become caught up in the Irish cause -- not as a question of politics, but as a matter of simple humanity. She comes to loathe the long imperial arm of England just as much as did Willie's mother before her. And in her daughter, Imelda, daughter of England and Ireland, she sees the tragedy embodied. The child chants: "Imelda Quinton is my name, Ireland is my nation. A burnt house is my dwelling place, Heaven's my destination."

They are all good, honorable poeple, but they -- like poor Ireland -- are victims of mere chance, arbitrary and random. Events over which they have no control seize them, hurl them about, leave them spent and shattered beyond repair. The most they can hope for is what, at the end, is given to Willie and Marianne and Imelda: a kind of peace, a bit of respite, a moment of quiet, the company of each other. But to the end they, like all of us, are mere fools of fortune; it was Willie's father's favorite phrase for others -- and he, of course, turned out to be a fool of fortune himself.

William Trevor has, in the short space of this novel, accomplished remarkably large things. Not merely has he dealt, seriously and thoughtfully, with important questions about the wisdom of love and the folly of war -- though never, in either case, does he discuss these loaded subjects with sentimentality or fatuousness -- but he has also created a small world that retains its beguiling magic even as it seems to be falling apart. He writes prose that is as exact in detail as it is felicitous in phrase, he maintains a nice distance from his characters that permits him dispassion as well as affection, and he knows how to bring a scene quickly to life in the mind of the reader.

These can be rather specialized gifts, usually found in the writer of short stories. But a writer of short stories is precisely what Trevor is, as can now be discovered by American readers in The Stories of William Trevor (Penguin, $8.95), a paperback that contains all the stories in his five previous collections. This collection, like Fools of Fortune, is a book to which your attention is urgently directed, for it contains as many satisfactions and surprises as there are to be found in life itself, told in voices so diverse and true that the mind is dazzled. To be a master of the story and a master of the novel is a distinction achieved by precious few writers, but such a master is William Trevor. CAPTION: Picture, William Trevor. Copyright (c) 1983, by Mark Gerson