I don’t know any true non-fiction books, but there are some great historical fiction novels for pre-teens out there. They usually are based off of facts, but some of the more sordid stuff has been taken out.
The one I remember reading when I was a kid (granted this was over 15 years ago) was the Royal Diaries. I’m sure they have more masculine themed ones too if that is what you’re looking for.
Here’s an Amazon link if you’re interested https://www.amazon.com/Elizabeth-House-Tudor-England-Diaries/dp/140015135X
I think the Royal Diaries book about Elizabeth I (https://www.amazon.com/Elizabeth-House-Tudor-England-Diaries/dp/140015135X) had a bit in there about Anne of Cleves - but it is a kids' book and I probably read it like 15 years ago, so not sure if I remember correctly...
Fun fact, I read this book when I was 9/10 and it made me interested in the history of CoE. Probably the reason I became Episcopalian when I reconverted, lol.