Before Imperium, I read two other books by Robert Harris, Fatherland and Second Sleep. They were both excellent, and I expected good things of this one. I wasn't disappointed.
Imperium is the first volume in a trilogy about the Roman statesman, lawyer and philosopher, Cicero (106 - 43BCE). It purports to be a biography in the voice of Tiro, his secretary, slave and friend, who he later freed. In fact, the historical Tiro did write Cicero's biography, but it's been lost to history.
This first voume covers Cicero's early career as a lawyer and politician in Republican Rome, as he worked to attain the rank of consul. We also learn a lot about Tiro, who invented an efficient form of stenography on clay tablets that made him invaluable to Cicero.
Two things in particular make this a very enjoyable novel. One is Harris' ability to conjure scenes so vividly that you feel as if you were there. There's something about knowing that pigeons roosted in the rafters of the Senate House that makes it real.
The other thing is his ability to make politics interesting, speaking as someone who doesn't usually read political fiction. The novel takes place against the backdrop of the great rivalry between aristocrats and plebeians, represented by Crassus and Pompey respectively. Meanwhile, Julius Caesar is plotting and scheming behind the scenes to take power for himself.
The politics of this period are eye-wateringly corrupt, despite there being laws against it. Cicero, as a decent, honest, yet ambitious lawyer, is drawn into the swamp. To give one telling example, there were three types of 'bribery agents', one to set up the bribe, one to hold the money (like an escrow account), and one to deliver it on completion of the deal.
As the novel progresses, it becomes more like a thriller, as Rome faces an aristocratic plot to take over the government and Cicero faces huge obstacles to becoming a consul. Genuine edge of the seat stuff.
I'm looking forward to reading the next volume, Lustrum.