Native New Yorker Jean Hanff Korelitz—whose fourth novel, Admission, was recently adapted into film—returns with You Should Have Known, a literary mystery.

Your protagonist Grace is a therapist who’s about to begin a promotional tour for her book on how people initially perceive but ultimately ignore their partner’s shortcomings until those shortcomings come back to bite them. What was the seed for this story?

I started thinking about what I’ve always been interested in: how people can’t see things that are right in front of them. All you have to do is read the papers to see endless examples of smart people who can’t see the nose on their faces. How could the partner of Bernie Madoff not have known what he was up to?

When I look back on a lot of my fiction, this question is hiding in there somewhere. I thought I should take it on straightforwardly this time and ask what it’s like to be that person who should really know better. I thought it would be more interesting if this person’s job involves telling people how to live their lives. That’s where it started. I began to think about Grace and how rigid she is and how settled she is in her ways. She’s smug about what she believes she knows about the world, and about her own life in particular.

Grace’s son Henry attends private school, and Grace feels out of place among the wealthy mothers. Was this something from your own experience?

I grew up [in Manhattan]. My sister’s [child goes to] the private school where we were both students and where my son is now, and I’ve been hearing from her for years about her experience and how frustrating it is because we both have such specific memories of the culture. Now it’s been altered, like everything else in Manhattan, by massive amounts of money. Years ago I read an essay in New York magazine about a woman who had grown up in Manhattan and how her income level had remained the same while the real estate’s been taken over by people with vast amounts of money, and how strange that was, and how kind of depressing it was. That always struck me. [Grace] seemed to be the kind of person who would send her own child to her own school and enjoy the sense of being the insider. That’s where that element came from.

After writing a book on the subject, do you have any thoughts on why people deny the obvious?

People need a narrative, and if there isn’t one on offer, they make one up. “Oh, he crossed the street because he doesn’t like me.” We always have an explanation for how people behave and why the world is. There’s a story, and sometimes it’s the story we have in mind, but usually it’s not. That leaves so much room for error.