John Keller is a hit man. He's also a regular kind of guy going through a midlife crisis. It is a bit bizarre to describe a book about murders and a paid assassin as being fun, but that's the word I used when I finished this book in 2005. Keller is a hoot! Recommended for fans of black humor.
I don't remember the plot well enough to write a summary, so here's one from Powell's:
Keller is a killer. Professional, cool, confident, competent, reliable. But he is also a complex person: Guarded and reclusive, icy and ruthlessly efficient, he is prone to loneliness and self-doubt, nightmares and career worries. He is known to his therapist as a "corporate troubleshooter," but Keller's real business is murder. He lives the life of a well-paid but lonely traveling businessman, a habitue of impersonal hotel rooms, bleak stretches of highways in rental cars, and anonymous eateries. A born New Yorker, he nonetheless fantasizes about the good life in the country, and in every place he visits, he dreams of setting up a home, away from the pressures and moral complexities his line of work entails.Hit Man, the first in a series, was published by HarperTorch in 1998. Robert Forster read the audio skillfully, adding to my enjoyment of the book.