A few things took Kirsten Miller by surprise in her 40s. One was when women her age would whisper the word menopause. “It’s like it was a shameful secret they could barely stand to acknowledge,” she says via Zoom from the sunny Park Slope, Brooklyn, apartment that she shares with her teenage daughter and their cat.

Another was that women in the New York advertising world, where she made her living for two decades, would hit their mid-40s and suddenly become disposable. “When you reach a certain age in the ad industry, you start getting what I call the nudge,” she says. “You know, ‘Thank you for your service, but maybe it’s time for you to go.’ ”

Miller speaks of friends who filed age-discrimination lawsuits because they were ousted from jobs when they were at the peak of their powers. “One of their lawyers told my friend almost all of his clients were women in their 40s and 50s, and the problem was just getting worse,” she says.

Miller’s new book, The Change (Morrow, May), is her first novel for adults after more than 15 years of writing YA and middle grade novels. Filled with disgust for men who slack, cheat, lie, grope, and appropriate women’s accomplishments, The Change has been described by Morrow as Big Little Lies meets The Witches of Eastwick, and it combines dark humor, mystery, and magical realism to express the rage that can burn particularly hot for women in midlife.

Set in a wealthy, fictional Long Island beach town, it follows Harriett Osborne, Jo Levison, and Nessa James—three women who have developed superpowers in middle age and have come together to solve the murder of a local girl.

“It feels very relevant,” says Rachel Kahan, Miller’s editor at Morrow, of the book. “As Kirsten has said, some of these stories are ripped from the headlines, which also makes it feel very satisfying, because here they come with a shot of witchery, revenge, and justice.”

The story opens with Harriett holed up in her modern masterpiece of a home. She hasn’t been seen since she received a pink slip instead of the promotion she was expecting at her ad agency, and since her husband left her for a younger woman. In the meantime, she has embraced her superpower—an ability to bend nature to her will—and turned her property into a jungle. The neighbors aren’t happy, and the president of the town’s snooty homeowner’s association visits to warn her that she’ll be fined if she doesn’t clean things up. The next morning, a giant plant with toothed leaves has consumed an entire flower bed on his front lawn.

Next we meet Jo, owner of a women’s gym called Furious Fitness. She’s filled with fury about her many experiences involving terrible men, and she knows about a rape cover-up at a hotel where she previously worked, dealt with an infuriatingly sexist banker when looking to finance her business, and endures an out-of-work husband who doesn’t pull his weight around the house. Jo’s superpower is harnessing the hot flash: she can literally burn things up with the grip of one hand, not to mention punch a hole in a wall.

The story’s primary protagonist, Nessa, comes into the story when she joins Jo’s gym. Nessa is a former nurse, the mother of college-age twins, and the widow of a police officer. Her superpower is hearing the dead, though she hasn’t in a long time. The story takes off when a dead girl starts whispering to Nessa about the location of her discarded body. Nessa heeds the call, Jo gets involved, and then eventually so does Harriett. The women harness their powers to set things right in a town (and a world) gone very wrong.

Miller, 49, never intended to become a writer. “Writing was always something I did for fun,” she says. “I didn’t ever imagine I could make money doing it. This was beyond my wildest dreams.”

She also didn’t consider herself a feminist, even after coming to Barnard College from rural North Carolina, where she grew up. Her mother, a math teacher turned realtor, was the primary breadwinner of the family and well respected in their community. She wore cowboy boots, blue jeans, and rode motorcycles. Miller described her as fair, but also terrifying and a total badass.

“It never even occurred to me that there would be a need for feminism,” Miller says. “I grew up in her shadow, and my father was her biggest fan. He was not going to tell his daughters that they couldn’t do anything. So I didn’t think feminism was necessary.”

Indeed, at Barnard, she remembers sitting in freshman seminars discussing the topic and thinking, “What the hell are they talking about? Why is this important?”

It wasn’t until Miller was in her 30s and working in Manhattan as an account strategist that she discovered men her age and at her same career stage were making substantially more money than she was. That’s when she realized how much harder women had to work to achieve success and what feminism was all about.

The inspiration for Miller’s first novel, In the Shadow City, came to her one morning when she was watching the news before work and saw that a giant sinkhole had opened up in front of a nursing home on Chrystie Street in lower Manhattan. “They took a rope, attached a video camera to it, and lowered it into the hole to see what was down there,” she recalls. “At the bottom of the hole was a perfectly preserved room from the 1900s.” Miller leapt off the couch and ran from her apartment on Ninth Street to see. “It was like a switch had flipped, and suddenly I saw the world in a very different way,” she adds.

Not long after, 80 pages of a novel about a second city below the streets of New York was born, along with the young spy, Kiki Strike, and a band of fearless Girl Scouts gone bad (aka the Irregulars). Miller wrote the book primarily to entertain herself, but mentioned it to a colleague at work whose boyfriend worked at Bloomsbury. He liked the initial draft and passed it along to an editor in the YA department, and they wanted it. Miller then signed on with WME’s Suzanne Gluck, who has been her literary agent ever since.

After completing 12 novels in 13 years, Miller says she felt burned out and couldn’t find the creative fire to write another book for a while. But watching the fall of cultural icons like Bill Cosby and Matt Lauer around the time that the #MeToo movement took off brought back that fire.

“I had been looking around, and I noticed all of the women my age were incredibly angry, furious, like, apoplectic,” she says. “It wasn’t something they could contain.”

She would capture this fury in a dark and yet funny way in The Change.

Gluck says that making the leap from the Kiki Strike books to writing for an adult audience made perfect sense for Miller, whom she calls “as wildly imaginative as her characters.” She adds, “Kiki Strike’s early readers have grown up and are ready for a gang of women who figure out how to right some wrongs in the world. And kick some ass along the way.”

Of the fan letters Miller has received over the years, she especially loves those about Kiki Strike. The main message of those books, she says, is that if you’re young and female, people are going to underestimate you. But when they do, you get the opportunity to take them by surprise and use that to your advantage.

“I’ve had a number of people write and tell me it was their first feminist hand book,” Miller says. “That makes me feel amazing.”

The Change takes that message to the next level, showing readers that tactic works even more powerfully for fully grown women at the top of their game .

Renée Bacher is a freelance writer whose work has appeared in the New York Times Magazine and the Washington Post Magazine.