Three Sisters, Three Queens - Philippa Gregory

When Katherine of Aragon is brought to the Tudor court as a young bride, the oldest princess, Margaret, takes her measure.  With one look, each knows the other for a rival, an ally, a pawn, destined - with Margaret's younger sister, Mary - to a unique sisterhood.  The three sisters will become the queens of England, Scotland, and France. United by family loyalties and affections, the three queens find themselves set against each other.  But as they experience betrayals, dangers, loss, and passion, the three sisters find that the only constant in their perilous lives is their special bond, more powerful than any man, even a king.