In 1474, a 23-year-old woman ascended the throne of Castile, the largest and strongest kingdom in Spain. Ahead of her lay the considerable challenge not only of being a young, female ruler in an overwhelmingly male-dominated world, but also of reforming a major European kingdom that was riddled with crime, corruption, and violent political factionism. The historian chronicles her life of Isabella of Castile as she led her country out of the murky Middle Ages and harnessed the newest ideas and tools of the early Renaissance to turn her ill-disciplined, quarrelsome nation into a sharper, modern state with a powerful, clear-minded, and ambitious monarch at its centre.