"Kathleen "Kick" Kennedy was the incandescent life force of the fabled Kennedy family, her father's acknowledged "favorite of all the children" and her brother Jack's "psychological twin." She was the Kennedy of Kennedys, sure of her privilege, magnetically charming and somehow not quite like anyone else on whatever stage she happened to grace. The daughter of the American ambassador to the Court of St. James's, Kick swept into Britain's aristocracy...