SECRETS OF MARIE ANTOINETTE by Olivier Bernier (Doubleday: $19.95). The secrets of Marie Antoinette, if anything can be said to be secret in the life of this much analyzed and scrutinized queen, are given us here in the form of the letters she exchanged with her mother, the Empress Maria Theresa of Austria. These begin with Marie Antoinette's departure at age 14 to marry the future Louis XVI of France and continue until her mother's death 10 years later. Thus, they span the last four years of Louis XV's court, dominated by the opposing forces of his last mistress, Madame Du Barry, and his three pious, aging, unmarried--and apparently unmarriageable--daughters, known collectively as "Mesdames de France," and the first six years of the new reign. Previously published more than half a century ago in French (the language in which they were all written, being truly the royal lingua franca of that era), they have been translated here by Olivier Bernier, who has augmented them with excerpts from the confidential dispatches of the Austrian ambassador in France to his sovereign, as well as a report from Marie Antoinette's visiting brother, Emperor Joseph II. Bernier, author of a biography of Louis XV, also provides substantial fore- and after-words, in addition to copious footnotes. It is a pity that he feels the need to be so strident in some of his annotations, because the text itself provides a vivid portrait of 18th-Century court life at Versailles and certainly offers the reader an unrivaled opportunity to gauge the personalities of the principals involved in this correspondence. One does not need to be told that the empress is shrewd, wise, hard-headed and manipulative when her every letter shows her to be so. As for her daughter, Bernier asserts, "As we read on, Marie Antoinette's very soul is bared to us; we understand why she was so beloved by a few, so hated by many, and how she came to her disastrous end." This is surely too extravagant a claim to be taken as seriously as its author apparently wishes. But he has done a service in making this source material so readily available to students of the wretched queen, and he has doubtless provided the many who continue to be fascinated by her with more to chew on.