The Three Crowns by Jean Plaidy
I've said it over and over again, but I really love everything I read by Jean Plaidy. Most of her books were published in the 60s and 70s (this one in 1965), and they're now being republished. Part of me wishes they would just republish all of them now, but the other part likes that they're slowly doing it so I can keep up and read them all gradually.
The Three Crowns tells the story of William and Mary of Orange, both who were niece and nephew to their uncle King Charles the I of England, Mary through her father the future King James II, and William through his mother Princess Mary Stuart. When the Catholic James II becomes king of England after his protestant brother's reign Mary and her husband depose her father to become the rulers of England themselves. Technically Mary is next in line, although she gives her husband the power which is why you're used to hear William and Mary of Orange compared to most other monarch's where their spouse isn't mentioned.
I know some can find history dull, but the amount of scandal involved (to start with the fact that Mary steals the crown from her father) I don't think it should be. But more than that Plaidy has a way of the stories coming alive. I have read some of her other books on Mary & William, so I was familiar with the story. But even though in a way I was reading the same basic story by the same author it still captivated me and felt fresh.
If you enjoy historical fiction in any way and haven't read Jean Plaidy I think you're missing out. I think that if this was your first book of hers you'd love it, although since it is 5th book in her Stuart series, it might make more sense to start with the first The Royal Road to Fotheringhay.
10 hours ago