Murder by Other Means (The Dispatcher, #2) by John Scalzi

Welcome to the new world, in which murder is all but a thing of the past. Because when someone kills you, 999 times out of 1,000, you instantly come back to life. In this world, there are dispatchers—licensed killers who step in when you’re at risk of a natural or unintentional death. They kill you—so you can live.

Tony Valdez is used to working his job as a dispatcher within the rules of the law and the state. But times are tough, and more and more Tony finds himself riding the line between what’s legal and what will pay his bills. After one of these shady gigs and after being a witness to a crime gone horribly wrong, Tony discovers that people around him are dying, for reasons that make no sense…and which just may implicate him.

Tony is out of time: to solve the mystery of these deaths, to keep others from dying, and to keep himself from being a victim of what looks like murder, by other means.