Texts that deal with realistic and in-depth ancient royalty, like Game of Thrones / A song of ice and fire?

Hi all, I’m both a history and fiction lover. Is there any books similar to A Song of Ice and Fire? I’d like a clear look at royalty, and adult themes (including real medieval threats, such as execution or torture). This can be a fictional book with fictional characters, or even in depth history books 🙂 thanks!