Florescu and McNally, both historians at Boston U., created the market for Vlad the Impaler (In Search of Dracula. 1972; Dracula, 1973; The Essential Dracula, 1979). Here, they bring his monstrous career to life once again in a detailed historical study. Although the authors start out in popular fashion, recalling how they tracked down the Dracula legend by following clues in Bram Stoker's masterpiece, this is in large measure a fact-choked history of geopolitical squabbling in 15th-century Eastern Europe. The Ottoman Empire threatened Christendom; into this tense, warring world rode Vlad Dracula, ready to impale at the drop of a pin. Young Dracula spent six years as a Turkish captive, an experience that the authors assert--in the hackneyed imagery that sometimes assails them--""toughened his character to a diamondlike hardness."" Back on home ground, Vlad murdered at least 40,000 during his rise to power. Although best known for impalement, he also favored boiling alive, decapitation, mutilation, live burials, and whatever else caught his febrile fancy. Finally imprisoned, he took to impaling birds and mice (the authors speculate that Vlad was ""partially impotent""); ironically, after his execution, his head graced its own stake in Constantinople. Although the authors, with breathtaking understatement, assert blithely that Vlad was ""on occasion guilty of senseless butchery,"" their moral condemnation comes through, as does the extraordinary richness of their research. Much too sophisticated for teen-age monster buffs, but a godsend for those wishing to place Dracula in historical perspective.