Amber Heard stars in “All the Boys Love Mandy Lane,” a movie made more than seven years ago that’s finally getting screen time. (RADiUS-TWC)

If Amber Heard looks a little dewier-cheeked in “All the Boys Love Mandy Lane” than she did in the recent “Machete Kills,” it’s not makeup, but mileage. Seven years have passed since “Mandy” first hit the screen at the 2006 Toronto Film Festival.

Why the delay between then and its current theatrical release in select cities (and simultaneously on demand)? It’s because the low-budget horror film, centering on Heard’s high school femme fatale, doesn’t fit neatly into any marketing category. It was something of a hit at Toronto, a launching platform for both arthouse fare and more mainstream movies. But after the indie-centric Weinstein Co. snapped it up, “Mandy” got panned at a subsequent New Jersey test screening and was immediately exiled to the island of misfit movies that nobody knows what to do with.

That’s a shame, because it’s eminently watchable. And I don’t even like this kind of stuff.

Clearly, its appeal has a lot to do with the film’s talented director, Jonathan Levine, who after this feature debut went on to make the cancer comedy “50/50” (a critical success) and “Warm Bodies” (a box office hit).

Levine brings a lot of visual style to “Mandy,” in addition to coaxing subdued, believable performances from his young cast. He also has a real knack for pairing music with images. “Mandy” features Juliette Commagere’s cover of the 1975 America hit “Sister Golden Hair,” along with Bobby Vinton’s great, cheesy 1972 classic “Sealed With a Kiss.”

The film’s setup and story are equally retrograde. After a prologue showing a violent tragedy at a high school pool party, “Mandy” gets down to business, fast- forwarding nine months to another party — this one at a secluded ranch — where the attendees are so obnoxious that you may want to kill them yourself, if they didn’t start dropping like bloody, mutilated flies.

Could the murderer be the mysterious caretaker (Anson Mount)? It isn’t hard to figure out, and the film, written by Jacob Forman, tells you whodunit anyway, at about the halfway mark.

So what the heck is the point?

This is probably what irritated the test audience. With the identity of the killer revealed, a lot of suspense — traditionally predicated on guessing who the psychopath is — evaporates. I’ll admit it: This initially annoyed me, too.

But then I readjusted my expectations and started looking for — and, yes, finding — other things to enjoy.

Heard and Mount deliver solid, psychologically interesting performances, as does the supporting cast of Whitney Able, Luke Grimes, Aaron Himelstein, Edwin Hodge, Melissa Price and Michael Welch. I’m not saying that these kids are tortured artists or that I didn’t want to smack them in the head a couple of times. But they’re a cut above the cardboard characters usually found in slasher flicks, even if, true to the genre, they also tend to get killed immediately after they’ve had sex.

Mostly, though, the film works — or doesn’t, depending on your point of view — because Levine hasn’t figured out that he’s directing a genre film, despite the boatload of cliches handed to him by Forman’s script. What ultimately made the movie click for me is that it doesn’t pander, avoiding as many stereotypes as it indulges. Thoughtful viewers may detect thematic whiffs of Columbine, blended with “Carrie,” that darken and complicate the film’s aroma of stale blood.

Thoughtful viewers? What kind of teen slasher movie is this? Too dumb for the arthouse, but too smart for the mall multiplex, the movie satisfies, paradoxically, precisely because it doesn’t deliver on expectations.

Will all the fanboys love “Mandy Lane”? Probably not. But some of them almost certainly will.

★ ★ ½

R. At the West End Cinema. Contains violence, blood and gore, obscenity, sex, nudity, drug use and underage drinking. 90 minutes.