If Carey Mulligan, the 24-year-old star of “An Education,” doesn’t nab an Oscar nomination come January, Nick Hornby, for one, is going to be sorely shocked.

“She’s absolutely incredible,” says the writer, on the phone from his home in London. “And you don’t look at that performance and think, ‘Well, that was her moment.’ You look at her and think, ‘Oh, she can do anything she wants to do.’

“There’s so much detail. She’s so alive. She’s so bright. You never get tired of watching her.”

Hornby, author of the novels “High Fidelity” and “About a Boy” — both nicely turned into movies — might be a tad biased. After all, his name is on the credits for “An Education,” a keenly observed, funny, sad coming-of-age tale set in early-’60s England that Hornby adapted from a memoir by Lynn Barber.

But the prolific scribe, whose new novel is “Juliet, Naked,” is not alone in his praise. Mulligan plays a fiercely independent 16-year-old (she was 22 at the time of shooting) who tumbles into a romance with a dashing cosmopolitan gent twice her age (Peter Sarsgaard). She grows up fast because of it.

And Mulligan, who was Kitty in Joe Wright’s “Pride & Prejudice,” makes the kind of leading-role screen debut that portends a long and fruitful career.

At first glance an unlikely project for Hornby, “An Education” was coproduced by Amanda Posey, who happens to be his wife.

“I had read Lynn Barber’s piece, which was originally published in Granta magazine,” Hornby explains. “My wife’s an independent producer, and initially I just read it and said, ‘You should do something with this.’ … She agreed, and when she started talking about potential screenwriters I began to feel possessive of the material. So I asked if I could have a go.”

Hornby, of a different sex and era (he turned 16 a decade later than Barber), nonetheless saw much in the memoir to relate to.

“There are all kinds of ways in which I identified with her, where I found points of personal identification with her story,” he says. “Notably, that feeling of being a suburban kid and wanting access to the city. The more drafts I wrote, the more I came to see it as a girl version of my memoir, Fever Pitch, which was sort of about the same thing.

“On top of that, it was funny and painful, and that mix is something that I’m always looking for if I’m trying to come up with my own ideas. I love the tonal switches. And then beyond that there were the things that I was very curious about: It described a world that I didn’t know very well — the ’60s before the ’60s, as it were. You know, a country really on the cusp of change.

“But I also recognized people, like her dad. He seemed to become the authentic voice of my country the more I knew him a bit. And then that bohemian underworld that she falls in with — I didn’t know anything about that. They struck me as really cool people, and interesting to write about.”

Amazingly, Hornby fit all of that and more into “An Education,” which has been deftly directed by Danish filmmaker Lone Scherfig and which costars Alfred Molina, Rosamund Pike, Dominic Cooper, Emma Thompson and “Rushmore’s” Olivia Williams. The film not only describes a young woman’s transition into adulthood but also documents a whole country’s, and culture’s, transition from postwar torpor to the heady days of Swinging London.

“An Education” took a while to get off the ground. There were false starts with another director, and the search for the right girl was arduous.

“Carey wasn’t cast that long before shooting,” Hornby recalls, “but she’d been on our radar for something like 18 months before we actually made the film. … But then the project fell apart for a while, and we tried to put it back together again after the director left. Then when Lone saw Carey, she was immediately convinced that she was the person.”

“We knew it had to be basically an unknown playing that part. There was no name English actress who could have done it. They’re all too old. That was one of the risks of the project, because we couldn’t ever go to a financier and say, you know, Keira Knightley wants to do this, or whomever. It just wouldn’t have worked.

“The only way we could ever get money was by saying, ‘This could be really good,’ which is never the most convincing argument.”