Megan Fox is the succubus and Amanda Seyfried is her bestie in Jennifer's Body.

This is the story of two teenage best friends, Jennifer (Megan Fox) and Needy (Mamma Mia’s Amanda Seyfried). They are like a real-life version of Betty and Veronica; Jennifer is brunette, sultry, and man-bait, whereas Needy is blonde, pretty, and always in her friend’s shadow. One night, they go out to a dingy bar, ostensibly to hear a band. Jennifer flirts openly with lead singer/guitarist Nikolai (Adam Brody). During the band’s first song, the bar catches fire, killing several people. Needy and Jennifer escape, but then Jennifer makes the bad decision to get inside the satanic band’s van. When she rematerializes the next day, she’s turned into a succubus who preys on male peers.

The joke, of course, is that she’s always preyed on male peers. The difference is that now she voraciously eats their flesh. It takes a while for Needy to catch on to what’s happening, and even longer to figure out a plan to stop it. Despite having a boyfriend, she secretly harbors some repressed sexual feelings for her friend, making her capable of falling under Jennifer’s spell too.

So you’ve got a couple of hot babes, plenty of gore, and just a smidgen of naughty teenage lesbianism. Yeah, Jennifer’s Body definitely works hard to be edgy. What sets it apart from most other horror movies that contain those ingredients is Diablo Cody’s dialogue. I was most amused by the way the film shows you some horrific bit of business one second (mutilated bodies, black succubus vomit, traumatized teens) then catches you off guard with a laugh the next. As with Juno, Cody shows an ability to create her own kind of hip patois. When Jennifer sneaks up behind Needy and says, “Where’s it at, Monistat?” you will either find it self-conscious and pretentious, or witty. I fall into the witty camp. Far too many horror movies these days barely even seem to have screenplays, since the writers appear more interested in dreaming up stomach-churching ways for people to die. It’s nice, then, to see one that actually tries to have some sort of perspective to it.

Jennifer is the role that Megan Fox was born to play. The character is sexy, stuck on herself, and a bit of a bitch. I don’t mean this as a slam against Fox. That said, her public persona is not exactly Little Miss Sunshine. Like a lot of vixens, she’s got a whiff of anger to her, and that quality serves her well here. There is a moment where Jennifer appears before Needy. She is covered in blood and looks like she is in shock. Very slowly, the dazed expression turns into something ruthless and blood-thirsty. No lie – I got a small chill up my spine. Fox may not have proven herself as an A-list talent as of yet, but she really makes this role work.

Having said that, Jennifer’s Body is really Amanda Seyfried’s picture. She’s terrific, giving the movie some sort of emotional grounding. If we care at all about what happens to Jennifer, it’s because we care about what happens to Needy.

I remember girls like Jennifer from high school. They seemed to have everyone in their pocket, knowing how to get what they wanted and how to make others respond to them in exceedingly positive manners. Those same girls also had a tendency to use boys and throw them away. It’s never blatantly hammed into you, but Jennifer’s Body is something of a metaphor for that skill (or, if you prefer, dark art). Imagine a version of Mean Girls produced in Hell, and you will have some sense of the film’s tone. Jennifer knows the power she has over others, who are awed by her looks and/or presence. She knows the power is not only over boys, but over Needy as well. When you stop and think about it, that’s a scary skill for a teenage girl to have. It’s perhaps not the carnage that is the scariest thing here; maybe it’s the casualness with which Jennifer unleashes it. Her savagery is the thing that makes her most fearsome. Becoming a succubus only frees the demon that was already inside of her.

The movie could have explored its intriguing ideas in even more depth, and it certainly doesn’t reinvent the wheel. Jennifer’s Body is still a better-than-average horror movie, and considerably more pointed too. Several moments are genuinely creepy. Other moments are darkly funny. Cody’s script - under the director of Girlfight’s Karyn Kusama, who brings a top-notch visual style - manages to combine those things into something that is a lot of wicked fun. The message: inside every adolescent girl is a figurative man-eater waiting to be unleashed. And inside every teen boy is a desire to be feasted on by the hottest girl in school. You can agree with that sentiment or not, but it may just define adolescent sexuality. If nothing else, it makes for a hell-raising good time at the movies.

( out of four)

Jennifer's Body is rated R for sexuality, bloody violence, language and brief drug use. The running time is 1 hour and 42 minutes.