The actor inside Casey Affleck

When British director Michael Winterbottom was putting together a film adaptation of Jim Thompson’s “The Killer Inside Me” — a notoriously brutal novel about a gracious Texas lawman who’s actually a sadistic murderer — he didn’t wonder long who should play the lead.

He thought immediately of Casey Affleck, and not because the lank, reed-voiced young actor projected any propensity for violence. Affleck’s reserved presence seemed right for the role of the twisted Texan, who moves through town like a reassuring brother while masking his homicidal intent.

“ Luke Ford has deliberately constructed this false persona for himself as the easygoing deputy sheriff,” says the prolific Winterbottom, whose film opens in Los Angeles on Friday (it’s already available on several video-on-demand platforms). “That’s what’s great about Casey. There’s a gap between what you see and what’s going on underneath.”

In person, Affleck, 34, is intelligent, polite, deeply curious and often opaque. Perhaps because he watched his older brother, Ben, work to cultivate a role as a celebrity and eventually get burned by it, Affleck the younger keeps a lot inside. “At the end of a movie,” says the actor, who typically avoids film festivals and other gatherings, “I feel like I never want to do it again.”

This low-budget indie is his first film since he emerged in 2007 with the one-two punch of “Gone Baby Gone” and “The Assassination of Jesse James by the Coward Robert Ford.” Those critically praised performances could have served as tickets to a very busy few years, with higher paydays in bigger studio films. Instead, Affleck chose to spend the years since making an obscure, eccentric documentary about the retreat from the limelight of his brother-in-law, Joaquin Phoenix, whose family has had its own issues with the seductive (and destructive) nature of celebrity.

Affleck, who comes across as more shy or reflective than calculated, is equally particular about publicity. When asked for his preferred location for an interview, he suggests a street corner at the foot of Pasadena’s Arroyo Parkway; it takes further negotiations to get him indoors, to a nearby coffee shop. Days pass where his publicist can’t locate him. In conversation he makes eye contact only occasionally, yawns, and offers laconic answers. But when discussing his passions — science-fiction novels, Kurt Vonnegut, the documentary tradition — he’s fully engaged and passionate.

“Although he’s a great actor,” says Winterbottom, “he’s a very reluctant actor. He’s offered a lot of stuff, but I think he finds acting something you have to plunge into. And he’s not always willing to plunge in.”

The careers of Casey Affleck and his older brother Ben resemble the story of the tortoise and the hare. The elder Affleck appeared in high-profile indies and won a best screenplay Oscar for “Good Will Hunting” while in his mid-20s. He went on to make big-budget popcorn movies, date Jennifer Lopez, marry Jennifer Garner and become a regular target for the tabloid press. Though he was praised for his performance as George Reeves in 2006’s “Hollywoodland,” his popularity as an actor seems to be in retreat. Casey, by comparison, has been a slow climber.

Raised mostly in Cambridge, Mass., he worked a bit in theater as a teenager, moved to Los Angeles to act at 18 (“a bust,” he says) and attended Columbia University but did not graduate. His film debut was as a dangerous teenager in 1995’s “To Die For,” alongside Phoenix, his future brother-in-law. Though he had small parts in a number of films, including “Chasing Amy” and “Good Will Hunting,” and a recurring role in Steven Soderbergh’s “Ocean’s” movies, Affleck broke out in a big way in 2007.

Looking to cast his directorial debut, Ben had to persuade his younger brother to take the lead role in “Gone Baby Gone,” based on a Dennis Lehane novel set in working-class Boston. (“It seemed like asking for trouble,” Casey says about it now. “I knew it would add some complications to have Ben directing [me], someone who wasn’t going to immediately do what he said.”) He plays detective Patrick Kenzie, who searches for an abducted child. The well-reviewed film earned both Afflecks special notices.

Winterbottom, best known for his films “24 Hour Party People” and “A Mighty Heart,” was especially impressed by the psychologically penetrating “Jesse James,” based on Ron Hansen’s novel. Affleck plays Robert Ford, a young sycophant who breaks into James’ gang before turning on his hero. Affleck was nominated for a supporting actor Oscar.

Affleck is generally protective of his older brother in interviews, and when asked about him, praises his intelligence, taste and leadership. Still, director Andrew Dominik told New York magazine that Affleck had excelled in the Robert Ford role because he “knows what it’s like to live in somebody’s shadow.”

“He certainly doesn’t want to be the center of attention,” says Jessica Alba, who plays a prostitute and Affleck’s love interest in “Killer Inside Me.” “He doesn’t want to be praised, told how brilliant he is. He’s just real complicated in his quietness.”

So far, “The Killer Inside Me” is best known for a contentious premiere at January’s Sundance Film Festival. Because the movie features several graphic scenes of Affleck’s character committing violence against women, some viewers walked out; at the Q&A afterwards, a woman greeted Winterbottom with: “I don’t understand how Sundance could book this movie. How dare you? How dare Sundance?”

“The violence is shocking in the book, and it’s shocking in the film,” the director responded. “The film has no sense of pleasure in the violence.”

Affleck, who was not at Sundance, says these scenes should hurt: “The violence is supposed to be upsetting.” But filming those scenes in Oklahoma was mostly tedious and uneventful. “They were … the least interesting of all the days of shooting. Most of the time you’re punching some blue mat off camera, or stopping a foot from their faces.”

Controversy aside, the novel is one of the exemplars of the second generation of noir literature — the wave that came after the breakthrough of Hammett and Chandler. Writer and critic Luc Sante describes the author’s work as “a link between popular literature and the avant-garde,” and Stanley Kubrick, with whom Thompson had two unhappy collaborations, called the 1952 novel “probably the most chilling and believable first-person story of a criminally warped mind I have ever encountered.”

The previous films made of Thompson’s work, including a 1976 Stacy Keach-starring “Killer,” have generally been unsuccessful. The two best-regarded were both directed by Europeans: “The Grifters,” directed by Stephen Frears (and adapted by Donald Westlake), and “Coup de Torchon,” directed by Bernard Tavernier from the novel “Pop. 1280.”

With “The Killer Inside Me,” the novel’s murderous narrator is himself a kind of cracked actor, conscious of his life as a performance. He describes himself as “standing outside myself” so long that he’s stuck in his role. “I’d pretended so long that I no longer had to.”

Affleck is exceptional at inhabiting this character divided against himself and at keeping us off balance: the film only works if we end up reluctantly sympathizing with this psychopath.

But his performance may not be enough to make the movie entirely work. Robert Polito, author of “Savage Art: A Biography of Jim Thompson,” praises Affleck’s acting. But he says “Killer,” which was written from Ford’s first-person perspective, shares a common attribute with other Thompson adaptations — an unwillingness to go deeply into the mind of its unreliable narrator.

“Some of it comes from the refusal of the directors to take on the voice of the main character and reduces the films to their violence and action,” Polito says of past attempts.

“There’s a lot to love about this film. But I was disappointed with the absence of thought in going into what makes the book exciting. It’s filmed too much like the book was written in the third person.”

Affleck, wearing a rumpled off-white shirt and faded jeans, is back at Jones Coffee, warming up a little. Just as he’s finally making eye contact, the air conditioner starts to rumble and shake and drips green fluid dangerously near his cup of tea

Instead of a Hollywood temper tantrum, the actor politely returns to the counter for more tea. As he resettles, he starts talking about a subject he’s far more comfortable with. “I love science-fiction,” Affleck says earnestly, explaining his fascination with Philip K. Dick, Stanislaw Lem and the early Vonnegut.

But he’s disappointed with most sci-fi films made since “Blade Runner.” “Where are the films? I don’t get ‘em, I don’t see ‘em. I never get a good science-fiction script.”

Most of Affleck’s recent energies, instead, have gone into his documentary about his brother-in-law, whom he refers to as JP (Affleck married Summer Phoenix in 2006; they have two small children.)

“I’m Still Here: The Lost Year of Joaquin Phoenix” looks at a period where the Oscar-nominated actor seemed to willfully sabotage his own career. The documentary — which includes scenes of coke-snorting, a search for call girls, defecation — has been shown to potential distributors; so far, the movie has no release date.

Nobody seems to know what this movie is — it is for real, or some kind of Andy Kaufman-esque prank? — including people who’ve seen some of it.

“I’ve never seen a movie about someone who was very, very private,” he says. “A very intimate portrait. I felt like I had a rare opportunity to do that. He’s not only very private but one of the most hardworking, talented actors alive.”

Of course, after Phoenix’s own breakthrough with “Gladiator” and “Walk the Line,” he retreated into a heavy beard and weight gain, turning his back on acting for a supposed rap music career, a time marked by his bizarre 2009 appearance on “Late Show with David Letterman” in which Phoenix seemed confused and unresponsive. “What happened to him during the two years I followed him were really interesting, and that I think will make a great movie.”

Affleck talks about his love of the documentaries of the Maysles Brothers (especially “Salesman”), the importance of finding your themes as a film unfolds, and the pros and cons of shooting copious footage — he says he’s shot 450 hours. But is this a real doc or a goofy mockumentary?

“There’s nothing ‘mock’ about it,” Affleck asserts, adding that speculation has grown “strange and twisted” because of his silence. “It’s just a film about a real man who had a period of his life that was pretty dramatic. In order to make the film I had to reveal certain private things and put them in the proper context. JP feels this will correct certain misperceptions.”

As for Affleck’s acting, he was slated to star in “The Kind One,” the adaptation of Tom Epperson’s recent novel set in ‘30s gangland L.A. But after problems with the script, director Ridley Scott moved on to “Robin Hood,” and it’s not clear how things will move forward.

“It’s weird with movies,” the actor says. “You get everyone excited, but you take one shot. If you lose momentum, it’s so easy to keep rolling down the hill.”

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Scott Timberg blogs on culture at https://www.TheMisreadCity.com