Is it an extended gossip column or is it a historical treatise? Don't ask the authors; they don't seem to know. The Princess Margaret/Anthony Armstrong-Jones story might seem grounds for gossip. Still, fact upon fact is presented in careful chronological sequence. Then again, the Royal Mother and others are described reacting privately, a characteristic of your basic spreader of the blab. There is no bibliography and only the photos are credited--prints, as it happens, with no particular pizzazz. The credit due the authors is for painstakingly compiling it all. They carry us through more than a century of royal facades that veiled terrible truths--from Queen Victoria's wayward son Edward to the Duke and Duchess of Windsor--with the apparent purpose of pointing up precedents for Margaret's behavior. But when we do arrive at Margaret, 30 pages into the book, her pre-Tony roguishness and her attraction to both Tony and, later, Roddy Llewellyn are treated with relative sympathy. Armstrong-Jones, for the most part, is presented in a favorable light as an imaginative, tradition-breaking photographer who demanded of his extra-marital partners that the affairs be handled discreetly or not at all. Throughout, dates and times are painstakingly supplied. ""The [honeymoon] yacht eventually sailed. . . at 5:33 P.M."" If anybody out there's interested in becoming an expert on the subject of Margaret's marital morass, this is their book.