"A Distant Mirror: The Calamitous 14th Century", Barbara Tuchman, 1978
It's not a royal book per se, but a historical narrative about Europe in the 14th century and has a lot of interesting stories about the royal families of that time.
It centers on the life of Enguerrand de Coucy, a French noble who married the daughter of the King of England and his conflict of allegiance when France and England went to war. His story is interesting enough but the rest of the book reads like a who's who of the Middle Ages. Edward, the Black Prince, Charles V (the first Dauphin and renovator of the Louvre) and Charles VI of France (the insane king who thought he was made of glass), the Duc du Berry who commissioned the incredibly beautiful Book of Hours, the Visconti family of Milan who commissioned the Visconti-Sforza deck of tarot cards, Henry V, and a bunch of non royal characters such as Chaucer, Petrarch, Sir John Hawkwood (English mercenary in Italy).
The women are by far the most interesting characters in the book. I felt a great deal of sympathy for Isabeau of Bavaria who was married to the mad Charles VI. When he was in his fit of madness, he couldn't recognize her and fleed from her thinking she was a ghost. Isabelle, the daughter of Edward III who married Coucy seemed like a spoiled rich kid, her father kept giving her titles and lands and she went through the money as fast as he gave it to her. The descriptions of some of her gowns with rich green velvet strewn with pearls and jewels together with a dozen of her matching ladies-in-waiting read like the medieval version of "The Lifes of the Rich and Famous" Against royal custom, when her husband gave up his English lands to fight for France, she separated from her husband and stayed with her father.
The author also writes a bit about Joan of Arc but she spends more time writing about the medieval woman chronicler, Christine de Pisan who made the name of Joan of Arc a household name. Christine's father and husband were minor court officials in the court of Charles V. When both of them died, Christine was left to earn her own living and turned to writing. She gained the trust of Charles V by writing a complementary biography of him but openly complained how women were treated by the male chroniclers of the time.
One of her books came about because she was despairing of great women to write about their deeds. A saint came to her in a vision reminding her of great women of the past. When Joan of Arc came upon the scene, Christine of Pisan was already waiting on a great woman to write a chronicle about and so she did, making her work the only major chronicle centering around a woman, Joan of Arc, and the only work written by a professional woman writer.
I haven't finished the book yet. Its rather long and the author throws so much detail and side stories in that its difficult to follow the story of Enguerrand de Coucy and his wife but overall its a fascinating and enjoyable book so far.