THE PROTAGONIST of Pauline Gedge`s Scroll of Saqqara (Viking/Penguin, 460 pages, $24.95 cloth) is Prince Khaemwaset, fourth son of Pharaoh Ramses 11 (1292-1225 B.C.) and "the greatest magician and physician in Egypt." Apparently, Khaemwaset leads an ideal life: he has a voluptuous wife, two loving teenagers, devoted servants, a magnificent home, and plenty of interesting work. Ah, but here`s the rub: that work involves opening ancient burial tombs and documenting their contents, and it`s led to Khaemwaset`s compulsion to one day uncover the mysterious "Scroll of Toth" with its two sacred spells, one of which "gives the power of bodily resurrection to the one who legitimately speaks it." When he does find an unusual scroll, all hell breaks loose, but slowly. The novel proceeds at a pace that`s as rich in atmosphere and detail as it is inexorable. Gedge`s strategy is to keep her readers in the dark at first, then to give us information in advance of her characters, and finally to whomp us over the head with a surprise ending, just when we thought all the magic tricks were out of the bag. Though as sexually fraught as any Harlequin, Scroll of Saqqara is also a conscientious depiction of a fascinating time and place.