"A GOOD STORY." That is how Kathleen Ken-

nedy's life and death struck Lynne McTaggart when she was invited to write it. Does the phrase sound a little chilling for something so poignant? There is nothing callous or sensational about the telling.

Kathleen Kennedy boarded the Washington on March 9, 1938, along with her family, for England. Her father was the first Irish Catholic ambassador to be sent there by the United States. A coup for the Catholic Irish. The family was mobbed by the press and 18-year-old Kathleen was mobbed by the "deb escorts," among them a fair sprinkling of aristocrats. She had been popular among her home set but this was an instant success.

Up till now she had seemed destined merely to extend the close-knit Kennedy clan by conventional methods. An heiress herself, she was almost engaged to Peter Grace, son of a shipping magnate. Her vitality made her seem cleverer and more beautiful than she was, though she had pretty red-brown hair and slim ankles that were to give her a start among the stout-legged English county girls. She was voted the "nicest" by the competitive Kennedys, and "niceness" was first and last her winning card.

McTaggart's portrait of the formidable Kennedy patriarch makes clear the source of Kathleen's first conflicts. Between family loyalty and personal identity. Her nickname was not "Kick" for nothing. There was always a sharpness, an independence, in fact a kick in her that marked her out. The author's word is "spunky." Yet at the same time there was this father, adored and adoring, supervising every moment of his nine children's lives, from their "regularity" after breakfast to their dating after dinner. "He would sit in his 'bullpen,' the terrace outside his second floor bedroom," writes McTaggart, "all day long and bark out deals." Would Kick tamely allow him to deal in her too?

There were already signs that Kathleen was diverging when the family was sent home on the outbreak of war. Ambassador Joe Kennedy was convinced that England would be "badly thrashed." Kathleen wept. She wanted to stay on.

Among her young British admirers who would fight against Hitler was Lord ("Billy") Hartington, son and heir to the ducal Devonshires of Chatsworth House. Hartington's father was a Cavendish, his mother a Cecil of Hatfield House--the two chief Protestant families in the realm and historically Ireland's greatest enemies. But Kathleen's friends knew nothing of politico-religious nuances. They assumed that Kick and Billy were "semi-engaged."

Meanwhile the conflicts that were focused on her father took two additional forms. Christian teaching on chastity was belied by Kennedy's own infidelities. (Kick handled this one with a defiant, "That's what all men do.") More subtly, no values, intellectual or spiritual, could stand up to Kennedy's worship of worldly success. For Kathleen, success could only mean "to marry well."

America's entry into the war gave Kathleen the chance to take London society by storm a second time, as a worker for the American Red Cross. One of her English friends said, "She's the best thing America ever sent to England." Billy and Kick rushed together again, Billy having been saved for Kick, it appeared, by parental opposition to a rival. By now, the "quiet rebellion" of Kathleen Kennedy against her father had erupted into overt mutiny against Mother Church. Despite the Church's then rigid teaching about mixed marriages ("mortal sin"), Kick and Billy were united in Chelsea Registry Office on May 6, 1944. Gardenias plus Devonshires arrived from Chatsworth but only a private blessing from Hyannisport. Nevertheless her brother Joe Jr. gave Kick away.

Her married life with Billy was to last no more than five weeks. A fortnight after D-Day, Captain Hartington embarked with his company of Coldstream Guards for Belgium. A born leader, he was shot dead by a German sniper on September 9.

Kathleen's love and marriage carried echoes of Romeo and Juliet. At any rate in what they each stood for, the Kennedys and Cavendishes were no less opposed than the Montagus and Capulets. And once the tragic wheel had been set turning its momentum was unstoppable. Within three months of the marriage, the stage was littered as if with Shakespearean carnage. On August 12 Kathleen's brother was killed, other close friends died, the husband of Joe's lover was killed two days after him. Pre-war values may no longer have seemed relevant to Kathleen.

Soon after the war she met and became the lover of Earl Fitzwilliam. If they had ever married she would again have "married well," for the Protestant Fitzwilliams were scarcely less grand than the Devonshires. How could Daddy complain? But Peter Fitzwilliam possessed one thing that Billy Hartington had been without when he fell in love with Kick: a wife. From the Church's point of view, Kathleen's former mutiny had become full-blooded revolution.

The wheel came full circle when Kathleen and Peter were killed flying to the south of France through a thunderstorm. It might be argued that but for Peter's reckless self-indulgence they would have taken the pilot's advice and waited till the weather cleared. But if Kick had missed that particular storm she would surely have hit others.

The personal story is well told, rising effectively to the dramatic finish. There is even something engaging about the author's occasional tone of Daisy Ashford in The Young Visitors ("champagne flowing in nearly every room") when negotiating the British social scene. The character assessments are not unfair, except for Mrs. Rose Kennedy. Kick's friends, we are told, criticized her mother for issuing a Mass card to pray for Kick's soul in purgatory. The author could have explained that this is a common Catholic practice and does not imply that Mrs. Kennedy regarded her daughter so exceptionally sinful. I also had a Mass card printed, with quotations from the Purgatorio, when a daughter was accidentally killed.

I cannot help wishing that Lynne McTaggart had limited herself to Kathleen Kennedy: Her Life without adding and Times. She gets the history of a former Hartington and Cavendish in Ireland thoroughly muddled. She refers to Russia as Britain's "ally" before the war; Hurricanes were fighter planes not "small bombers"; and workmen in 1938 were not pouring concrete into Buckingham Palace for a royal air-raid shelter, since even after the palace bombing of September 9, 1940, the king and queen were still sheltering for a time in a housemaid's cupboard in the basement.

Debrett's Peerage is thanked for being the author's bible in this project. But like the other Bible, you have to know how to use it. It has proved a capricious guide to these rambles among British titles. To name only one confusion: Edwina Mountbatten, wife of Earl Mountbatten of Burma, was never known as "Lady Edwina Mountbatten." After her marriage to Lord Louis she became Lady Louis Mountbatten; and after the earldom was conferred on him she became Countess Mountbatten, usually known as Lady Mountbatten.