McCreight unravels secrets of murder and domestic drama in A Good Marriage (Harper, May.).

Where did the inspiration for this story come from?

Being married myself for 18 years, and being surrounded by many friends who have been married for as long, or longer, was the starting place. I thought how different each marriage seems—the balance of power, the ways of communicating, how affection is expressed. It made me wonder, are those couples all happy? Undoubtedly, you can’t know the truth about a marriage unless you’re living inside it. Other details for the story are drawn from several sources. For instance, I’m a recovered alcoholic and got sober after I was married. Managing an addiction in marriage—which is often complicated in ways you might not expect—is always something I’ve wanted to explore. And, certainly, a lot of inspiration comes from experiences living in Park Slope, where partner-swapping parties do happen!

Which character was most challenging to flesh out?

Probably Lizzie, the main character. In a weird way, all my characters end up being pieces of me. Because Lizzie is most similar to me, I made certain assumptions that readers will know her as well as I do. I needed to get to the nuance of who she is, specifically, so it took me a long time to separate her from me and get the subtleties of who she really is.

How do you create plot twists that are shocking but also plausible?

It 1,000% comes from revision. I don’t work from an outline, so in my very first draft, I reveal all the twists. Then I keep revising to make revelations more mysterious and work through about 10 to 12 drafts. You can’t “unknow” the twists, so you start testing them out with fresh readers. It becomes a delicate balance, because you get to the point as to whether you should include one little sentence. Will that piece of fact reveal too much? I strive to make emotionally satisfying twists by ensuring that they’re organic to each character. That way, the twists don’t feel arbitrary and readers don’t feel manipulated.

What message do you want readers to take away from your book?

There’s no single truth about what makes a good marriage. It’s uniquely different for each couple. Trust, communication, loyalty, openness, kindness, generosity, fidelity—these are all excellent ingredients. But there’s no one recipe for success where marriage is concerned. It’s important for readers to dispense unrealistic expectations and get past societal expectations. Marriage is ultimately grounded in the vagaries of love—always an uncertain endeavor.