Grace

Proper, demure and wholesomely beautiful, Grace Kelly was quite the opposite of what she seemed, according to this seductive biography. Lacey (The Kingdom) writes of ``the eruptions of sexuality that she usually managed to conceal behind her virginal exterior.'' The book is likely to be much discussed, less for the story of Kelly's family background, film career and marriage to Monaco's Prince Rainier than for its startling details of sexual promiscuity before and after her marriage. Lacey captures the pageantry of the 1956 marriage, then focuses on the somewhat sleazy reality behind Monaco's charming facade and its easily bored, practical-joking ruler. The author's description of Princess Grace's passivity before her unappreciative husband and spoiled daughters will also surprise readers. ``When fairy tales do not finish happily,'' he writes, ``their ending often tends to be cruel.'' In his examination of the road accident that led to the princess's death in 1982 at age 51, he turns up some unpleasant possibilities. Photos. 100,000 first printing; major ad/promo; first serial to Vanity Fair; Literary Guild main selection. (Sept.)