Even after a full day of phone interviews promoting his new movie “American Ultra,” Jesse Eisenberg manages not to sound rote or weary.

“Easiest part of my job,” he says perkily, describing the New York City hotel room in which he is ensconced as “really nice.”

Eisenberg, who has two films in theatrical release right now, seems really nice, too — and really modest. The 31-year-old actor best known for his Oscar-nominated performance as Mark Zuckerberg in 2010’s “The Social Network” says he doesn’t know why he’s been offered such wide-ranging roles since his breakout as the sensitive son of a divorcing couple in 2005’s “The Squid and the Whale.”

“I would never cast myself in anything,” he said, sounding a bit like one of the directors he most admires, Woody Allen. “I feel like the completely lucky beneficiary of the imaginations of other people who think I can do it.”

Eisenberg, whose face seems to perpetually wear an expression of concern, plays very different parts in his two movies out now. In “The End of the Tour,” a Sundance fave getting critical raves, he portrays journalist David Lipsky, who shadows the late author David Foster Wallace for four days on a national book tour. In “American Ultra,” opening Aug. 21, he’s a stoner convenience store clerk who discovers he was actually trained as a government agent with a particular set of deadly skills. The movie is a mashup of three types of gritty-indie subgenres — action film, comedy and romance.

“I was shocked they could successfully blend all these elements,” he said. “The comedy was good, the action surprising and engaging, and the romance sweeter than most romantic scripts I read. But what I liked most is that my character remains consistent in every scene, no matter how different.”

Tackling action scenes

Eisenberg, who soon begins shooting his second film with Woody Allen, also takes a turn playing one of the all-time great villains, Lex Luthor, in “Batman v. Superman: Dawn of Justice,” coming out in March.

“The sets were massive and the scenes very theatrical and dramatic, but always at the heart of it was getting to play a real character who can exist outside the context of the movie,” he said. “It felt like an off-Broadway play in that way.”

Despite the many types of roles Eisenberg has tackled, he’s mostly known as a brainy brooder. “American Ultra” tested his action-scene mettle more than any previous film experience.

“The old cliché in theater is, if you’re nervous, pick up a prop, which will immediately take you outside of your mind. My character is so intense and visceral I was always distracted in the best way.

“There’s no way to fake jumping off a refrigerator or fending off three guys trying to kill me at the same time.”

A key element to what makes “American Ultra” work is the easy intimacy between Eisenberg and Kristen Stewart, who plays his love, Phoebe. The two first worked together on the 2009 amusement-park comedy “Adventureland,” and recently did an amusing gender-switch parody on sexism in publicity interviews, with Eisenberg answering vapid questions typically asked only of actresses.

Eisenberg calls Stewart “as good as it gets.”

“She prioritizes authenticity to such a degree that when we were in ‘Adventureland,’ when she was 17, she would call ‘Cut!’ if she felt like she was lying. She also has a great sense of humor. Something few people can do well is to make a scene funny not by behaving in a funny way or being dramatic, but subtly, without missing the irony. She can reconcile those things, which is even more rare in someone as famous as she is.”

On Wallace and writing

Fame, and ambivalence about it, happens to be the subtext of the David Foster Wallace movie “The End of the Tour.” Namely, Wallace has achieved sudden fame and Eisenberg’s character — a struggling novelist — is jealous of it.

“Wallace was very hesitant about dipping his toe into the pool of public notoriety,” Eisenberg said. “He spends his life writing, a solitary experience, and then puts himself out there for public consumption in a way that makes him feel very vulnerable. My character is desperate for that kind of attention, so he feels both in awe of and in competition with Wallace. That’s the emotional thrust of the movie.”

The film did a bit of shooting at the Mall of America. You’d think, with the Queens-raised Eisenberg’s city-indie sensibilities, he’d turn up his nose at such environs. Wrong — he loved it there.

“I felt like I had landed on another planet,” he said. “I did a lot of browsing. If you grew up in our family, that’s our version of shopping. We filmed in places that weren’t yet open for the day, so it was exciting to be in one of the most populated places on Earth when it was quiet. Some really beautiful visuals.”

Eisenberg speaks like a writer, in complex, well-articulated sentences, so it’s not surprising that writing is his other passion. In addition to three plays, he has a short-story collection titled “Bream Gives Me Hiccups” coming out this fall. He cites George Saunders, David Sedaris, Miranda July and his friend Simon Rich as influences.

“With my acting, I don’t get roles that are exclusively funny, but I really love writing humor,” he said. “I also like writing about loneliness and emotional delusions. My book is a collection of characters and situations that bring out the absurdities of life, the net effect of the anxieties of being a person in the modern world.”