Veteran celebrity-biographer Edwards (Wallis, 1991, etc.) does her best with Prince Rainier and his ancestors, but the Grimaldis as a dynasty seem more bent on survival than on cutting a heroic figure. Europe's oldest dynasty was founded in 1215, when wealthy Genoese merchant Rainier Grimaldi established a fortress on the rock that was to become the heart of the principality. The place was soon under siege from a rebellious nephew; and during subsequent centuries the rulers of Monaco have had to contend with threats from family members, neighboring France and Italy, and magnates like Aristotle Onassis. The Grimaldis also once held the title of ""prince of France,"" which endowed the family with great prestige and proved especially useful during those centuries when marriage to a very rich woman was the only form of respectable entrepreneurship open to improvident aristocrats. As absentee landlords who preferred to live in Paris, the Grimaldis neglected Monaco itself--that ""sunny place for shady people,"" as it was once described by Somerset Maugham. Not until a Princess Caroline of the mid-1800's had the brilliant idea of building a casino did the principality become wealthy and self-supporting--though this solution wasn't exactly approved of by such people as Queen Victoria, who refused to visit the Grimaldis in their palace. Extravagant and apparently prone to making bad judgments (Prince Rainier's grandfather saved the family and his fortune by collaborating with the Nazis) and bad marriages (Edwards excepts the marriage to Grace Kelly), the family has lurched from one scandal and financial disaster to another, though Edwards feels that the present prince, decent and well-intentioned, is doing good things for his family and country. Competently written and researched, but, apart from the Grace Kelly years, the Grimaldis come off here as a rather shabby and dull lot.