Sharon Kay Penman good reads about Llewelyn the Great and King John…
If you read I, Claudius, you have to follow it up with Claudius the God. The edition I have (Penguin, I believe) has both in one book.
Only a novella but The Fireflies of Port Stanley is a good read. Not fiction, but again a short and good read is A.C.A.B All Coppers are Bastards.
Hilary Mantel - Wolf Hall and Bring up the Bodies
You could do a lot worse than Ken Follett’s The Pillars of the Earth. (And possibly the follow-up, World Without End, though I haven’t read that yet.)