In his new novel, “Imperium,” the British author Robert Harris fictionalizes Cicero’s less-known early career as a young lawyer on the make. He paints an engrossing picture of the caldron of Roman politics and presents a Cicero for our own times, a man who is the lineal ancestor of the modern career politician.

The result is an experiment as bold as it is unexpected: a novel that draws so scrupulously on the Roman source material that it forgoes much of what are traditionally regarded as the prime features of the thriller. Although there is detective work, there is no detective; although there are twists and turns, there is rarely any artificial ratcheting up of suspense. Instead, Harris trusts to the rhythm of the republic's politics to generate his trademark readability, a rhythm that the Romans themselves enshrined in their literature as something relentlessly exciting: in short, a thriller. Genres ancient and modern have rarely been so skilfully synthesised.