Italian author Roberto Costantini introduces mercurial Rome Commissario Michele Balistreri in his debut thriller, The Deliverance of Evil—the first of a trilogy.

Did your engineering background help you plot such a complex novel?

Planning is part of my mindset; it’s part of my life. My wife was very upset because the house was full of flow charts. But then the planning has to stop when you start writing. If the character doesn’t want to do what you planned, you need to rearrange the plan.

Judging by The Deliverance of Evil, there’s much more on your mind than whodunit.

Each book in the trilogy is a classic thriller because you have many suspects, you have the person who is investigating, and in the end, you also have the murderer. But the nontraditional part, the part that was more interesting for me, is the story that goes across the three books. That’s the story of a family, and through this the story of Southern Europe from the ’60s until now.

With his explosive temper and callousness toward women, Commissario Balistreri isn’t an easy guy to like.

Many writers build a central character that has some bad characteristics—he drinks too much, or he’s a womanizer, or he’s violent, or whatever—but in the end the author describes him so that people will like him. I purposely put some things in Balistreri’s character so that people will really dislike him. I think the truth does not necessarily come out of good people. The association that, in a thriller, it has to be a good guy who finds the truth has nothing to do with reality. I actually believe that most people who are very good personally would not be able to find a murderer. In order to be able to identify with somebody who kills, you yourself cannot be entirely that good. So I think it is important that, in the end of The Deliverance of Evil, the investigator is not so different from the murderer.

Why?

A little bit of violence is in everybody. I’m not talking about only criminals. In 99% of people, this violence remains there for their entire lives and nothing happens. In 1%, by mere chance, it explodes and things go beyond control. The real violence that we have to fear is not from serial killers—it’s the diffused, small violence that is inside each of us, because of the fact that we are not happy.

Were people you know surprised by the novel?

Absolutely, 100%. When they heard I was going to publish, at first they all thought it was going to be a management book.