Don’t hate him because he’s beautiful.

So much has been made of Fish Tank star Michael Fassbender’s rugged good looks, which have earned him comparisons to a young Daniel Day-Lewis, that it might be tempting to dismiss him as just another pretty face. Yet to witness his harrowing depiction of late Irish Republican Army militant Bobby Sands in last year’s Hunger is to appreciate his dedication to craft.

For that role, Fassbender, 32, shed roughly 40 pounds off his already slender frame to play Sands, an imprisoned agitator who died in 1981 while participating in a well-publicized hunger strike. (That’s not all Fassbender lost. The actor, born in Germany and raised in Killarney, Ireland, says the rapid weight loss also robbed him of his libido – temporarily.)

American audiences might best remember Fassbender as Lieutenant Hicox, the suave British spy who meets a bloody end in Quentin Tarantino’s Inglourious Basterds. Currently, he’s starring opposite newcomer Katie Jarvis in Fish Tank, Andrea Arnold’s eagerly anticipated follow-up to Red Road (2006). The subject is Mia, a rebellious 15-year-old girl mired in a dead-end life.

Fassbender plays Connor, the casually seductive older man who gets past her defenses with the promise of a better life. In a moment of drunken recklessness, they sleep together. Is Connor a pedophile, or simply a man of extraordinarily poor judgment?

“People throw around the word ‘evil,’ but that’s such an abstract concept,” he says. “I’m not even sure what it means. I don’t think he’s a predator, and I don’t think he’s premeditating. He definitely abuses a position of trust, but I didn’t want to portray him simply as a bad guy.

“He brings a lot of positivity into Mia’s life. He gives her confidence and encourages her to follow her dream to become a dancer. She’s not getting that at home. But he crosses a line. I wanted to make him seem like a normal guy, not a monster. He makes a terrible decision, and we’re all capable of that – it’s in all of us. If people are shocked or repulsed, maybe it’s because they’re afraid they could do something like that themselves.”

On accepting his role in Fish Tank, script unseen:
“It comes down to the director. I’d seen what Andrea was capable of in Red Road, and what I really like about that film is that she doesn’t judge her characters at all. She doesn’t put them into safe boxes, making obvious heroes and villains. Her characters are more ambiguous than that, and her stories leave you with something to think about. I knew I had to work with her, regardless of whether I’d read the script.”

On working with Jarvis, who had no prior acting experience:
“We didn’t do any rehearsals. Andrea prefers to film her rehearsals because she likes working in some sort of chaotic and unstable atmosphere. And in that environment, Katie was incredible. She has naturally what a lot of actors work very long and hard to find, which is the ability to grasp the truth in a scene. She works without vanity or pretense. She has a very intuitive approach that serves her well.”

On mentoring inexperienced actors:

"I think it's a very dangerous thing to do. The most important relationship is between an actor and a director, and if any coaching is to be done, that's the director's job. It's not my place to offer advice, and Katie certainly didn't need any."

On the similarities between Arnold and Tarantino:
“Besides being very passionate about their work, they both create a very liberating environment for their actors. They’re very clear about what they want, but they afford you the opportunity to try new things and see what works.”

On the movies that inspired his passion for cinema:
“It was the American cinema of the 1970s that made me want to become an actor – The Godfather, Dog Day Afternoon, Raging Bull, The Conversation. You can’t go wrong with any of those. I’ve always been a huge [Martin] Scorsese fan, and I’d love to work with him. Or, more recently, Paul Thomas Anderson, or the Coen brothers – The Big Lebowski is one of my all-time favorites. There are so many directors I’d like to work with. Can you put in a good word?”

Fish Tank is playing now at the Lumiere Theatre in San Francisco and the Shattuck Cinemas in Berkeley. It is also available via Video On Demand.