The Calling by Neil Cross (Luther #1)

Meet DCI John Luther in the prequel to the epic series Luther, starring Golden Globe winner Idris Elba.
He's a murder detective. A near-genius. He's brilliant; he's intense; he's instinctive. He's obsessional. He's dangerous.
DCI John Luther has an extraordinary clearance rate. He commands outstanding loyalty from friends and colleagues. Nobody who ever stood at his side has a bad word to say about him. And yet there are rumours that DCI Luther is bad - not corrupt, not on the take, but tormented. Luther seethes with a hidden fury that at times he can barely control. Sometimes it sends him to the brink of madness, making him do things he shouldn't; things way beyond the limits of the law.
The Calling takes us into Luther's past and into his mind. It is the story of the case that tore his personal and professional relationships apart and propelled him over the precipice.
Beyond fury, beyond vengeance. All the way to murder . . .