Damn these are good!
I'm 5 or 6 novels into the series now. While they've all been entertaining, two of them ("Roman Blood" and "Catalina's Riddle") are superlative.
You can think of them as "Forrest Gump in Ancient Rome". The lead character, Gordianus the Finder (a detective), gets himself involved with the major events and scandals in the late Roman Republic. All the major players get involved: Cicero, Sulla, Caesar, Catalina, Pompey, Crassus, Clodius, Mark Antony, etc.
They're impeccably researched. He doesn't change any known (or presumed) facts. Especially impressive is the way he handles slavery. They're certainly not preachy books, but Saylor doesn't let you forget the whole economy is based on slaves.
I'm not saying he's Robert Graves or anything, but if you're interested in Ancient Rome, you won't go wrong here.