A fascinating political thriller, based on the rise of Cicero to the consulship in 63 B.C. Harris manages to capture the characteristic rhythm of Cicero's sentences, their many clauses, their frequent appositions, but never bogs down in tiresome pedantry. His Cicero is, I suspect, rather more pleasant and entertaining than the man.
As Hornby observed in The Believer, Harris has a knack for avoiding anachronistic exposition. Historical fiction writers tend to have characters explain things that nobody would talk about, because everyone (in their time, or their world) already knows. Harris almost never does this. (At one point he does give way and lets a character remind us who Tiberius Gracchus was and what happened to him, but even Homer nods.) His Romans are always Romans, but they never stop to think about how Rome is ancient or explain things for 21st-century witnesses. Remarkably little needs to be explained, anyway.
Though Harris is at some pains not to underline this, the struggle to preserve the Roman constitution against Pompey, Crassus, and Caesar bears a startling similarity to the struggle to preserve American civil liberties. When Pompey erects beacon stations along busy river roads, supposedly to provide warning against pirate raids but actually as security theater to show worried voters that something was being done, the specter of contemporary airport searches and subway announcements is impossible to suppress.