In For You and Only You (Random House, Apr.), Kepnes’s series protagonist, murderous psychopath Joe Goldberg, enrolls in a Harvard writing fellowship.

What inspired Joe’s creation?

I went through hell for a couple of years, where my father died slowly from cancer and my mom was sick. My dad had a dark, sardonic sense of humor, and Joe’s voice was a way to give my family a laugh, to bring my dad back to life in a sick way he would have appreciated very much and find something good to do with all that sadness. I also wanted to explore what it means to be a survivor. Joe is a survivor, but that doesn’t necessarily mean he’s a good person.

Do you have a psychology background?

When I was in high school, my guidance counselor was like, “I’m going to give you this test, the triarchic theory of intelligence. If you do well, you can go to Yale for the summer.” So, I took the test, and I got to go to the program on a scholarship. The theory was, there’s three types of intelligence, practical, analytical, and creative. They never told us what we were, but supposedly, if you take someone creative and put them in a practical classroom, they won’t do as well. It was basically a college-level seminar studying case files of abnormal people and criminals. I just ate it up. I remember feeling like I had found what I wanted to do. When I got to college, I learned I liked psychology, but not the graphs and that aspect of it. So, I designed my own major, Notions of Normalcy in American Culture, and that allowed me to study psychology, but also creative writing.

Were you hesitant to satirize your own industry?

Of course! The self-consciousness was extreme. But it’s from Joe’s perspective—I can’t say that enough. There was a lot of, “No, this isn’t you! I love you!”

Is Joe’s head an uncomfortable place for you to be?

With this book, in particular, it was really hard, because the subject matter is so close to home. I was like, okay, this is Joe, he doesn’t have good experiences; he blames everyone but himself, and picks apart everything. I hope what happens for me happens for the reader, where you’re in his head, find yourself relating to an impulse, and then take a step back, like, “Whoa! No!”

Your series inspired a hit TV show. What’s that like for you?

To hear people out in the world talking about your imaginary friend, and to have a human being associated with him—it’s endlessly surreal.