Cullen’s The Sisters of Summit Avenue (Gallery, Sept.), features two competitive sisters: one is a struggling farmer, while the other works as a “Betty” writing recipes for Betty Crocker.

What kind of research did you do?

I went to Minneapolis to find Betty Crocker, because in the 1930s, people were really encouraged to go to her kitchen and meet her. What struck me was that they would get to the kitchen and would be gently told there are actually 21 “Bettys,” not one Betty Crocker. They kept boxes of tissues around the kitchen because people would inevitably break down and cry. It crushed them. I went to the headquarters in Minneapolis and I thought I could at least go see some memorabilia about her, but no, there’s nothing. So I felt like those people going to the kitchen to see her and who were disappointed. For some reason, that really resonated with me and made me want to write about her.

The novel deals heavily in themes of want and desire. What message do you hope readers to take away in that regard?

One of the reasons I was interested in setting the novel during the 1930s was the rise of radio and, with it, the rise of advertising. It’s fascinating how advertising picked up this burning desire we all have to be better than people, to be classy, to have more than your neighbors. Betty Crocker was a part of that during that era—helping you be the best cook, and to get your man and keep your man happy. The sisters are part of this new way of driving consumption. One is very aware of being a have-not and the other’s job is to encourage people’s desire for hot breakfasts and yachting luncheons. It was important for constructing the story, I really wanted to talk about appreciating what you have while you have it. It’s such a human thing to want more and something different. It’s good to improve yourself and to have curiosity. But to always want more? And to lord it over someone else? That’s the toxic part.

Did you think about social class while writing?

I’m very interested in class and how we don’t talk about it. We’re very conscious of it, and it’s very painful for the have-nots, like June and Ruth. In June’s case, she thought having status would make her feel better about herself. But we know when you rely on that to make you feel better, you can never have enough. And Ruth is always comparing herself to her sister. She sees something she wants and she hurts her sister, who she loves more than anybody in the world. They have to realize you can never have enough, and to look at what you already have.