Lawrence Block 
Hit Man 

Keller is your basic urban Lonely Guy.He makes a decent wage, lives in a nice apartment.Works the crossword puzzle. Watches a little TV. Until the phone rings and he packs a suitcase, gets on a plane, flies halfway across the country…and kills somebody. It’s a living. But is it a life? Keller’s not sure. He goes to a shrink, but it doesn’t work out the way he planned. He gets a dog, he gets a girlfriend. He gets along.