The Prince of Darkness — Jean Plaidy

The untimely death of Richard the Lionheart left his nephew Arthur and his younger brother John in contest for the throne of England. Reluctantly the barons chose John, and so began years of rule by a ruthless and greedy tyrant. Yet despite his reputation, John, still manages to seduce the young and beautiful Isabella of Angeloume. But in taking her as his bride he makes an enemy for life. And in the tempestuous years that follow many men come to believe that the House of Anjou was tainted by the Devil's blood, the loathsome monarch was himself Evil Incarnate, the very Prince of Darkness...