NEW YORK – Despite living the public life of a global celebrity, her personal life routinely splashed across magazines, Nicole Kidman finds the strength to perform by shrinking her world.

“Acting is actually very private,” says Kidman. “My husband (country singer Keith Urban) is a performer and he goes out and performs in front of 15,000 fans. That’s just not my calling; I could never do it.”

Kidman, now 40, stars in two films this fall, beginning with Noah Baumbach’s “Margot at the Wedding,” the young director’s follow-up to 2005’s “The Squid and the Whale.” Later this December, she will lend her star power to the big-budget fantasy epic “The Golden Compass.”

As Margot, though, she gives an exceedingly raw performance of a woman in crisis. A novelist and single mother, her character is brutally honest and neurotic to the extreme.

Although the film, which has an intentionally unpolished, ’70s aesthetic to it, has received mixed reviews, Kidman’s performance is a welcome sight for fans of the actress whose work since winning an Oscar for 2002’s “The Hours” has been checkered with duds like 2004’s “The Stepford Wives” and 2005’s “Bewitched.”

It can be difficult to put a finger on what’s made Kidman such a star. (She regularly fetches $17 million or more for a film, though she worked for scale on “Margot.”)

New York Times critic A.O. Scott once wrote that the secret to her appeal is the “plucky, disciplined indomitability” she brings to her performances. Film critic David Thomson, who wrote a book last year about Kidman, has called her “the bravest, the most adventurous and most varied” actress of her time.

Neither explanation would seem to jibe with Kidman’s description of herself as shy. But it could be Kidman’s particular blend of reticence and abandon that has helped build her acting reputation. Even when she throws herself fully into a role, she maintains a mysterious distance, whether in Stanley Kubrick’s “Eyes Wide Shut” (1999) or as Virginia Woolf in “The Hours.”

“For me, it’s a very, very private, very intimate place to exist, and I do that with a director in a small little bubble,” she said during a recent interview. “And that suits my personality, which is a little more introverted but still in huge desire of sharing ideas and intimacies and secrets and all of those things. I like the delicacy of acting.”

Kidman, who was born in Hawaii but raised in Australia, is the daughter of a psychologist and a nurse.

“I spent my childhood in hospitals,” she says, suggesting her youth bred an empathy for all types of people. “Because I’m creative, that’s where my path as an actor has led me, to show all the different walks of life.”

Kidman began acting in Australian films, but became known to American audiences with 1990’s “Days of Thunder,” where she met Tom Cruise, her former husband of 10 years. Her breakout performance was in 1995’s “To Die For,” but through the ’90s, many perceived her only in relation to her famous husband.

Their divorce in 2001 coincided with Kidman’s most successful period, artistically and commercially. She starred in Baz Luhrmann’s “Moulin Rouge!” and “The Others” in 2001, and followed up those movies with the career-making “The Hours” as well as Lars von Trier’s “Dogville.”

“I’m curious. I will remain curious. I want to be brave,” she says, explaining what she laughingly calls her “erratic” choices. “I’m not interested in what I know. I know what I am and what I’m capable of, so I’m not interested in exploring those things.”

Kidman, who had two children with Cruise, married Urban in June of last year – an event which, along with Urban’s subsequent trip to rehab, kept Kidman in the tabloids. She recently confided to Vanity Fair that she and Cruise early on lost a baby, leading them to adopt. She also said she was briefly engaged to someone after Cruise, but declined to name him.

“You know, I have trouble believing that people are that interested, and then I see myself on the cover of a magazine and I go, ‘Oh, why did I say that?’ or ‘I didn’t say that!'” Kidman says. “That all seems a little foreign and out-of-reach in a way. That’s probably why I live in Tennessee.”

She and Urban have recently bought a rural parcel of land, though the actress will be Down Under finishing Luhrmann’s epic romance “Australia” until the end of the year. Knowing that the large production was next on her schedule, Kidman was eager for a film like “Margot.”

“I wanted something small that was all just about performance, the intricacies of performance,” she says. “I wanted to do something where I was in the hands of somebody that I really trusted and I didn’t feel like I was having to lead the ship. I was able to sit back in an ensemble group.”

The person she trusted, Baumbach, says that though Kidman happens to be a star, “she got there by having a really enviable acting career.”

“I just love watching her,” says Baumbach. “She will often not do the same thing from take to take. It was very kinetic and very intuitive. She would really feel her way into a scene. You could see it. She’s not afraid to try things and get it wrong.”

Though Kidman has said she’d like to have a baby with Urban, she insists she’s not about to take a long break from acting.

“I’m not someone who’s just going to lie down in the backyard,” she said. She eagerly rattles off her goals: doing a play, making a “really powerful political film,” making a film that “shocks people again.”

“I would like to walk through my life saying, ‘Maybe I took a lot of risks, but I’m glad I took them,'” she says. “‘I’m glad I didn’t take the easy way out.'”