Liane Moriarty wasn’t sure “women’s fiction” applied to her books. “Part of my unconscious belief was that it’s a somewhat lesser genre,” she says. A literary spare rib, if you will. Besides, who ever refers to “men’s fiction,” anyway?

Classifying her books as “thrillers” doesn’t seem right, either. That would involve an unexpected corpse or two. Also, Moriarty says, “I don’t always feel like there has to be a twist,” although many of her books contain a few.

Fortunately, her works no longer require categorization. Liane — pronounced “Lee-AHN” — Moriarty dwells in that exclusive club, publishing’s glistening penthouse, a place few authors will ever enter. She writes fat, succulent, don’t-bother-me-I’m-reading blockbusters that regularly top bestseller lists.

“I feel the need to point out that this happened before the beautiful people got involved,” Moriarty says on a call from her home in a suburb of Sydney, where she lives with her partner, Adam, a former farmer in Tasmania and now stay-at-home dad, and their two children, 11 and 13.

Sure, since her 2014 novel “Big Little Lies” became a smash HBO hit three years later, the beautiful people have become profoundly involved in Moriarty’s work. But her success stretches beyond it: In nearly two decades as a published author, she has sold 22 million copies.

Moriarty’s ninth novel, “Apples Never Fall,” will be published Tuesday, with a massive first printing of 750,000 and a virtual book tour. Television rights have been bought by Heyday Television, run by the producer of the “Harry Potter” film series, “Once Upon a Time in Hollywood” and “Marriage Story.” No word on who will star, but given Moriarty’s strong connections to Nicole Kidman and Reese Witherspoon, the odds list toward a decidedly A-list cast.

“Apples Never Fall” delivers what Moriarty’s readers have come to expect, a Vegas buffet of plot: a 69-year-old mother’s sudden disappearance, a potentially culpable husband, their four former tennis prodigy children and, for good measure, an unnerving stranger who enters the parents’ home and refuses to leave. To outsiders, the Delaneys appear to have everything — a happy marriage, towering height and athletic prowess — but, like the women of “Big Little Lies,” also cope with epic dysfunction and a hailstorm of secrets.

The book arrives while “Nine Perfect Strangers,” based on her 2018 bestseller about a woo-woo wellness center that has returned to the bestseller list, streams on Hulu. It stars — who else — Kidman, who has become the author’s patron saint of premium cable. In turn, Moriarty has become the star’s limited-series muse. The Australian ectomorph, who calls the author “a national treasure,” says she and Moriarty — both 54 — have “become incredibly close, as much through life’s events and our families as through her writing.”

Since the success of “Big Little Lies,” the novelist has enjoyed the luxury of casting as she writes, creating characters with specific actors in mind. When Moriarty was asked to write a novella as the basis for the 2019 second installment, “I had never written a sequel to one of my novels and I wasn’t sure I should be involved,” she says. “I definitely wrote it with the show in mind. I wrote it with an American accent.” Her sister, Jaclyn, also a novelist, advised, “Why not have fun with it?” Why not write a role for the most honored thespian on Earth?

Moriarty obliged. She gave Kidman’s mother-in-law, a pursed-lip wellspring of passive-aggressive behavior, the birth name of a certain actress who has been nominated 20 times for an Oscar, thinking “I wonder if they’ll notice that I called her Mary Louise? I thought that very clever.”

They noticed. Meryl Streep accepted the role and proved especially withering in her takedowns of Reese Witherspoon. (“I find little people to be untrustworthy.”)

In an early draft of “Nine Perfect Strangers,” the novelist had “a small bald man called Gregory” running the Tranquillum House wellness retreat. Well, where’s the fun in that? “I changed Gregory to Masha, made her 6 feet tall and — there you are — nobody could play the role except Nicole,” Moriarty says. Kidman was right there to grab it. “Liane told me she was writing a character in her next book for me to play,” the actor writes from Australia. “Based on what she said about Masha, without even having a manuscript to read, we bought the rights. It was a little impulsive, but that says something about the faith we have in Liane.” (The series inspired a Tranquillum House pop-up in a Los Angeles mall, presumably without the mind-bending smoothies.)

While you’re at it, the novelist wondered, might Melissa McCarthy play Frances, the insecure mess of a has-been author? “I honestly didn’t think I’d get her,” Moriarty says, but get her she did. Kidman, an executive producer of “Nine Perfect Strangers” (Moriarty is one, too), also secured the rights with Australian producer Bruna Papandrea to two earlier titles, “Truly Madly Guilty” and “The Last Anniversary.”

During the pandemic, Moriarty discovered that she had breast cancer, detected “just after I had delivered the manuscript for ‘Apples Never Fall,’ ” she posted on her Facebook page. The final radiation treatment was Aug. 6. In a phone interview a few days earlier, Moriarty made no mention of her health. In conversation, she is polite but circumspect (though a call between two strangers and a 14-hour time difference may not lend itself to intimacy).

“I knew from the beginning my prognosis was good. But I was very distressed for a while, and I kept tying myself up in knots, analyzing myself: Why are you so upset? You know you’ll be fine,” Moriarty writes in a later email. “It was as if I was looking for a deeper, more complicated reason to be upset. I never found one. I was just upset that I had cancer. It was better when I finally accepted that.” Cancer didn’t cause Moriarty to rethink her life or work: “I definitely have not had any ‘seize-the-day’ type epiphanies.”

Little appears to outwardly bother Moriarty long-term or inflate her ego. She’s a big deal in Australia, a country that doesn’t tend to glorify big deals. “We call it ‘Tall Poppy Syndrome.’ Our job is to keep each other grounded,” she says.

The eldest of six, Moriarty grew up in a family where writing was rewarded — literally. “Our father liked to tell stories and he would commission us to write them, $1.50 to fill up an exercise book,” says her sister, who is known as Jaci. “It made us feel like it was a legitimate and serious occupation. His philosophy was: ‘Do what you love, then the money would follow.’ We learned how to commit to a story and see it through to the end.”

This is not what happened. For years, Moriarty successfully worked in marketing and advertising, “sitting in my office with my big shoulder pads.” Jaci, who writes novels for young adults and adults, became the first Moriarty to publish, with “Feeling Sorry for Celia” in 2000.

“I felt happy for her because I love her dearly but I was filled with envy,” Moriarty says. “I had a kind of rage for myself. I could not say that I was trying and was rejected. I hadn’t given it a proper shot.”

For that, “I’m eternally grateful,” Moriarty says. Her sister’s success became the push she needed. Moriarty’s first novel, “Three Wishes,” was published in 2003. Since then, she has produced a book every two or three years. Another sister, Nicola, writes domestic thrillers. The other siblings, Moriarty notes in her website bio, “have no interest in writing and they really love it when people say, ‘Are you one of the authors?’ ”

People often tell Jaci “I’m so tired and it’s your sister’s fault. I was up until 2 a.m. reading.” Moriarty and Jaci supply each other writing prompts, while claiming first dibs on real-life anecdotes they wish to fictionalize. “Apples Never Fall” started with an idea from Jaci about a “bike lying on the ground with apples all around it,” says Moriarty, which became the opening scene.

From those apples, a 480-page novel grew, one about a family of tennis players with very little tennis in it. There is no obvious role for Kidman though everyone in the clan, save the missing mother, is six feet or taller.

Moriarty no longer minds if her novels are categorized by gender. Women’s fiction doesn’t seem like a lesser genre anymore. “Why not embrace that? Yes, it’s women’s fiction,” she says. “Women are the majority of my readers, and they buy lots and lots of books.”

Profile: Liane Moriarty

“Apples Never Fall.”

Henry Holt and Company. 480 pp. $28.99