Hmm, I mostly read books set in Ancient Rome (late republic) and I agree with the above comment that they're almost always political. Looking at my shelf, perhaps "Counting the Stars" by Helen Dunmore is something. It's a romance novel about the poet Catullus and Clodia Metelli (commonly believed to be his mistress). Catullus hates politics, so there's not a lot of it :)

A book I really enjoyed recently is "The Song of Troy" by Colleen McCullough, which retells the Torjan War from beginning to end. Some great character portrayal (Odysseus and Agamemnon come to mind first) and some very interesting interpretation of the Iliad :)

My favourite historical novel would be, hands down, "The Ides of March" by Thornton Wilder. It features politics and the beginning is a bit tedious, but in my opinion it's really worth it. Very vivid portrayal of Caesar, Cicero, Catullus and lots of others.