Has there ever been a less appealing paramour than Adam Sackler, the boyfriend of Lena Dunham’s character on HBO’s Girls? As played by Adam Driver, 28, he’s a parody of a Brooklyn hipster douche — an often shirtless, occasionally employed, completely weird actor-carpenter living in the far reaches of Brooklyn, with few responsibilities besides sexually debasing Dunham’s Hannah Horvath and treating her heart “like monkey meat,” as she says. “He’s full of id,” says Driver of the character. “Very animalistic, a caged animal, like a rhinoceros running full force in one direction until he’s exhausted, and then he tries something else.”

Surprisingly enough — or not, depending on what you think about how women are seduced — Sackler held on to Hannah, and even became unexpectedly charming in the final episodes of the show’s first season. Now he’s not only beloved among many female viewers, a kind of contemporary Mr. Big, but he’s Hannah’s real, honest-to-God boyfriend (according to him, all she had to do was ask). But which way the pendulum will ultimately swing on their relationship is anyone’s guess, and Driver’s wobbly answers to inquiries on this topic on a recent weekday afternoon don’t offer much guidance. A perfectionist and gentle giant with a will of steel, and a man of extremes himself, Driver is hanging around his compact, parlor-floor apartment in the “second-oldest building in Brooklyn Heights, or at least that’s what a tour group said when they were passing by,” he says. The living room is decorated mostly with found or one-of-a-kind objects: a chartreuse mid-century chair that he bought on the street for $60, a log that fell nearby during Hurricane Irene, a used upright piano from Harlem (he plays Rachmaninoff, though he wants to get better at jazz). It’s a beautiful space, simple but with immense care taken to put exactly the right thing in exactly the right place.

Driver sits at a brushed-metal coffee table in tan moccasins and a gray shirt that’s one shade off from his slacks, talking about his childhood. He grew up in Mishawaka, a town in northern Indiana, where he landed lead roles in school plays, though his mother, a paralegal, pulled him if he didn’t make honor roll. After high school, unsure what to do, he sold vacuums and was a telemarketer for a waterproofing company. Acting seemed more appealing, so in 2001 he tossed his possessions into his Lincoln Town Car and set off for the City of Angels, but he was broke inside a week. Back in Mishawaka, “I got a brochure for the Marine Corps and threw it in the trash,” he says. “In the heat of an argument, my stepdad said, ‘I want you in the Marine Corps. And I was like, ‘No — uh, maybe.’ ” He smiles. “I figured if I was going to go into the military, I might as well choose the toughest path.”

To his surprise, Driver loved the Marines. “I never had the sports thing where I tested my manhood and was a guy and all that stuff before then,” he says. “In retrospect, it’s amazing acting training because you’re locked with 30 guys your age living this Greek lifestyle, very aware of death, not feeling so immortal. It’s an interesting atmosphere in which to learn a little bit about human behavior.” He actually looked forward to fighting in the Middle East and was devastated when he wasn’t deployed after breaking his sternum in a mountain-biking accident. “I started loading up on hydrocodone and lifting weights because I wanted to go so badly,” he says.

After an honorable discharge in 2004, Driver was back in Indiana. He enrolled in the University of Indianapolis on the G.I. bill, dreaming about being at war, writing e-mails to his buddies. “I checked up on their wives, too — I was the only one they trusted,” he says. Acting was now really becoming appealing. He went to Chicago for an off-site audition for Juilliard with a Richard III monologue (at the time he hadn’t even read the play). “I’d worked up a lot of confidence from the Marines — ‘Oh, I’ve been with the best, so I’ll go to Juilliard because it’s the best,’” he says.

Since graduating in 2009, Driver has acted in many Broadway and Off Broadway plays, including Angels in America; he’s currently shooting Girls’ second season and is scheduled to appear in Steven Spielberg’s Lincoln and the Coen brothers’ Inside Llewyn Davis, about New York’s sixties folk scene. “For me, becoming a man had a lot to do with learning communication, and I learned about that by acting,” he says. “Emphasis in the Marine Corps isn’t on talking about your feelings. But as I found myself being able to use my words, I became less aggressive as a person, less angry.”

Driver works on his roles on a couch in this apartment, and keeps to a strict regimen of exercise and eating well, which includes six eggs every morning, though he throws away four of the yolks. “It’s good for you, protein and all that,” he says. “I used to eat a whole chicken every day, for lunch. I did that for four years. But it got tiring — go to the store, buy it, eat it. It’s a mess.”

For a while, he thought he’d remain on the stage. He even passed on his Girls audition at first. “TV’s the devil, whatever, but then I read the thing,” he says. “Lena is a very rare writer, very unpretentious. When things become precious or sentimental, that kills it for me.” He hasn’t thought about Girls’ first season for a while. “We filmed so long ago, and got so intimate with each other, that it almost feels like a weird art project in someone’s basement that no one would ever see,” says Driver. Nor does he think much about the meaning of the Sackler character, in terms of sexual politics or otherwise. “I only think of the show in terms of trying to make the most emotional sense possible out of the scenes we’re playing. I’ve never gone into work thinking, What does this mean?” On set, they generally filmed what Dunham had on the page but also tried some of his suggestions. How many made it in? “I don’t know,” he says. “I haven’t watched the show. I saw the pilot, and I learned my lesson. I can’t help but see the mistakes.”

Click below to see more pictures of Adam Driver from the New York magazine shoot.

This story appeared in the June 25, 2012 issue of New York Magazine.