Margaret George doesn't have many books, but all of them are both a treat to read, and a time commitment to read. They're always very long, but they also always flow well and are absorbing. She will take a major historical figure, usually name the book after them, and write about their lives from their own point of view. It's "historical fiction" in the sense that she endows them with their own thoughts and emotions, and will occasionally do things like consolidate four minor characters that served a similar function into one, or invent a minor character to illustrate something important and real. But it's meticulously researched, and she infers the thoughts and emotions based on real events.
For example, it's not hard to imagine that if you were flirting with a guy, and your cousin hauled off and married him, you would feel pissed off at your cousin, and maybe never speak to her again. It's also plausible that if you got to know the son of your cousin years later when he was an adult, your feelings towards him might be complex, carrying both the weight of your anger towards his mother and your long-stifled love for his stepfather. Especially if you were a virgin queen, married to your realm.
This is where we pick up the plot of "Elizabeth I." As Margaret George notes in the afterword, few British monarchs hold such a continued sway over public imagination. You can look at her and see many things, and people felt that way even in her lifetime. It must have been a daunting task to try to write from her perspective, and there were so many tacks she could have taken, since Elizabeth I reigned for so long and had so much happen. But the primary plot of the novel concerns Elizabeth I and her cousin, Lettice Knollys Devereaux Dudley Blount. Lettice was banished from court when she married Robert Dudley, and when the book opens, she and Elizabeth I have not seen each other in years. Robery Dudley dies soon after the book opens, and that's when Elizabeth I gets to know his stepson, Robert Devereaux, the Earl of Essex.
We see from both Lettice and Elizabeth's points of view as the book wears on. Robert Deveraux is the thread that binds them together, and although Lettice at first seems like a typical stage mom whose only hope is her offspring, her character evolves. Elizabeth is a bit harder to categorize, which I guess meshes with history. Though this isn't my favorite of Margaret George's books, it's still a good read, and I'd still reccomend it.