Assassins Anonymous by Rob Hart

 It looks like a typical AA meeting--people tell their stories in search of support to changes their lives. And it is, except the people are professional assassins and they're trying to  follow a new path that doesn't involve killing people. Mark (aka The Pale Horse) is one of the attendees. He stays after the meeting to clean up--and is stabbed by a Russian assassin who sneaks up on him. Mark manages to escape and gets medical help from a former medic named Astrid, then he, Astrid and his cat are on the run, trying to figure out who the Russian works for and why they are trying to kill him.

It's a fascinating look at the life of a professional hitman who realizes that the choices he's made have cost him the love of his life and any sense of security--which is why he wants out even though someone is clearly trying to keep him in the game. Great summer read.