The Constant Princess by Philippa Gregory

The Constant Princess tells the story of Katherine of Aragon, Queen of England, Henry VIII's first wife. It tells her story from her point of view, starting at age 5 in a siege encampment outside of Granada with her parents, Queen Isabella and King Ferdinand of Spain. She has been betrothed to Prince Arthur of England since the age of 3 and is called the Princess of Wales. Her destiny is to become Queen of England and even at the tender age of 5, she knows it and is determined to hold it. At the age of 15 she sets sail to England and to her wedding. Things get off to a rocky start, but she soon falls madly in love with her new husband and they begin planning what they will do when they are made king and queen. Unfortunately, Arthur dies only 5 months into their marriage, but he extracts a promise from Katherine that she will marry his brother and become queen anyways. She never breaks this promise, although it is many years before she finally succeeds in keeping it. She eventually marries Arthur's brother Henry, who was a spoiled child and turns into a very spoiled man and king, and she pretty much singlehandedly keeps her husband in line (for awhile at least) and the kingdom safe from the Scots and running smoothly.

I loved her determination in a male dominated world to become the woman her mother was, to be a Queen Militant and not just the woman who does whatever her husband says. I also loved how she learned that not everything her mother believed was right and how she chose to not make the same mistakes her mother had made.