Writer-director Richard LaGravenese’s film, based on the first novel in the young adult series by Kami Garcia and Margaret Stohl, oozes Southern Gothic eccentricity and some amusing if inconsistent touches of camp. (A droll, drawling Jeremy Irons sitting at the piano playing Chopin? Margo Martindale in a feathery hairclip, carrying a live peacock? Yes and yes, please.)

But a strong cast of likable and, yes, beautiful actors can only do so much with the formula in which they’re forced to work. And, like the “Twilight” movies, the special effects are all-too often distractingly cheesy.

The setup breathes some new life into such familiar material, though, as co-stars Alden Ehrenreich and Alice Englert feel like actual awkward teens enjoying the fraught thrills of first love rather than slick, ironic kids who are too cool. Their first meeting, on a two-lane road during a downpour, has all the trappings of a romance novel but it’s also an early indication of the lively chemistry they share.

Once the plot machinations start grinding in the second half, though, “Beautiful Creatures” as a whole grinds to a halt. Spells and scenery-chewing can be a hoot; watching other people sitting around scouring ancient tomes for clues, not so much.

Ehrenreich’s character, 17-year-old Ethan Wate, grew up in the suffocating small town of Gatlin, S.C., and is dying to get out. He rebels against the local conservatism by reading all the banned books he can get his hands on, from “Slaughterhouse Five” to “Tropic of Cancer,” and as he enters his junior year in high school, all he can think about is how far away he can go to college.

But the arrival of the mysterious and equally restless Lena Duchannes (Englert) makes Gatlin suddenly tolerable. She’s come to live with her uncle, Macon Ravenwood (Irons), a descendant of the town’s founders and an alleged Satanist who never leaves the moss-covered and heavily gated Ravenwood Manor. The popular, Bible-thumping socialites instantly hate her so naturally, Ethan is intrigued — and the fact that Lena introduces him to Bukoswki only makes her more exciting.

It turns out that Lena is — duh, duh-duh-duh! — a witch, or rather a “caster,” as her kind are called in the vernacular. And at a ritual on her 16th birthday, she’ll find out whether she’s destined for goodness or evil. Her attempts at functioning as a normal girlfriend until then, full of stolen kisses and Friday night movie dates, bring a sweetness and relatability to these wild proceedings.

Eventually, though — as in the “Twilight” movies — “Beautiful Creatures” introduces more and more supporting characters to add to the denseness of the complicated, overly explained mythology. Emma Thompson feels a bit too shrill in not one but two menacing roles, Viola Davis exists solely to provide exposition along with her usual grace, and a radiant Emmy Rossum vamps it up with reckless abandon as Lena’s sexy cousin, who has long since gone to the dark side.

Ehrenreich, who made such an impression a few years back in Francis Ford Coppola’s “Tetro,” has a goofy charm about him that makes him attractive but also seemingly accessible; when I first saw him, I thought he had a young Leonardo DiCaprio thing going, but as he gets older he seems to have acquired an impishness in his eyes and smile that are reminiscent of a young Jack Nicholson. And Englert, the daughter of acclaimed director Jane Campion, has a natural beauty and directness about her that are appealing.

She doesn’t sparkle in the sun — instead, she shines from the inside. And she will again someday with better material.

“Beautiful Creatures,” a Warner Bros. release, is rated PG-13 for violence, scary images and some sexual material. Running time: 123 minutes. Two stars out of four.