The first was Imperium by Robert Harris. Yes, it's a typical Robert Harris. I leave it with that.
Another calibre is The Classical World: An Epic History from Homer to Hadrian by Robin Lane Fox.

Historians might gripe about one or the other detail. However, I'm none of them and highly enjoyed the read. I'm now also updated about the importance of buggery in the various phases of the Classical World. Just in case time travel will ever make headway.