Emo is literally evil in Jennifer’s Body, Diablo Cody’s follow-up to her Oscar-winning Juno script. This horror/comedy hybrid—in which a teenage groupie is impregnated by demons—busts more than a few stereotypes. Its dorks aren’t virginal. Its slut doesn’t die. (Technically.) And Megan Fox, the Transformers-launched It Whipping Girl, proves capable of carrying a movie on her supernaturally good-looking shoulders.

In fact, if an actress other than Fox had been cast as the titular succubus, Jennifer’s Body might be a bit less compelling than its present good-but-not-great incarnation. Her much-ballyhooed beauty makes it seem entirely plausible that animalistic man-eating is what causes her to be “really pretty and glowy,” according to her nerdy best friend, Needy (Mamma Mia!’s Amanda Seyfried). When Fox is onscreen, you can’t take your eyes off her. And even when the beast within Jennifer is hungry, making her “ugly—well, ugly for her,” Fox’s got the kind of face and teeny waist that keep on giving.

At the beginning of the film, Jennifer is just another eye-rolling cool girl at a high school in backwood Devil’s Kettle, Minn. Despite her cheerleader status at the top of the student pecking order, she hangs out with the bespeckled Needy, who’s been her BFF since they were little kids. (They even each wear a locket so inscribed, trinkets that have a laughably important role at the film’s climax.) Needy has a sweet boyfriend, Chip (Johnny Simmons), but Jen’s on the prowl, one day pouting until Needy agrees to go with her to see some crappy indie band named Low Shoulder at the local dive because its singer (Adam Brody) is “extra salty.” (Remember, this is Cody’s acrobatically slanged universe.)

The group doesn’t even make it through the first song when a curtain catches fire and the place burns down—a not-too-subtle and somewhat distasteful reference to the deadly 2003 fire at the Station, a Rhode Island club. The girls escape, and Jennifer isn’t too rattled to hop in the band’s tinted-window van. The next time Needy sees Jennifer is in her house in the middle of the night. Except she’s bloodied and vacant, and tears into a chicken she finds in Needy’s fridge before letting out an inhuman roar and a spew of inky vomit.

The next day in school, Jennifer’s fine. “You have a tendency to overreact,” she tells her freaked-out friend. When Needy shows her blackened fingernails as proof that the projectile puking actually happened, Jennifer suggests a manicure: “You should find a Chinese chick to buff your situation.”

Jennifer’s Body may cool the anti-Cody movement’s vitriol; invented hipsterisms are significantly toned down compared to Juno, and in fact the script’s biggest weakness is that many of the characters sound the same. More important, though: Horror fans will likely be bored. There’s gore, but not a high body count. Cheap scares are even rarer. But director Karyn Kusama (Girlfight) adds a nice style to the frights that, along with Fox, keep the film interesting even when it dips into predictable OMG! territory. Arresting zoom effects underscore Jennifer’s supernaturally heightened senses, for example, most notably in the instance of her first kill. Another gut-tearing murder is shown in silhouette. And it’s always cool when Jennifer, Prom Queen shows flashes of Jennifer, Satan’s Pawn—the catlike eyes, the sudden levitations, and those ungodly roars.

Cody’s injections of comedy may not match Scream deftness, but the tonal shifts rarely seem out of place. (When Needy’s boyfriend asks if she noticed the make and model of the band’s van, she says, “I don’t know—an ’89 Rapist?”) The state of indie rock gets its deserved share of kicks—Low Shoulder’s reasoning for dabbling in the Satanic is hilarious. But then there’s the resolution of the story, which is too ridiculous and too easy. Even diehard Cody fans will have to admit that the film’s finale jumps the pitchfork.