When Kami Garcia heard that Jeremy Irons would be in the film version of her book Beautiful Creatures, she thought she was getting punked. Garcia is a much bigger fan of the actor than her co-author and best friend, Margaret Stohl, and for Garcia, there was no one on earth she’d rather have playing Macon Ravenwood, the wise and good-hearted incubus and a main character in the novel. So when Stohl informed her that Irons would indeed be playing that exact part, Garcia was skeptical.

But the news was published in Variety, and that meant it was real. And Irons wasn’t even the first A-list actor to join the film. Viola Davis and Emma Thompson had already signed contracts.

This was just the tip of a strange iceberg for the Young Adult writers, who say they’ve been experiencing “different phases of crazy” ever since the process of adapting their hit book to the big screen started. It was nutty from the get-go — the women clinched a film deal even before their book was actually published. And when Garcia and Stohl visited the film’s New Orleans set and saw everything they had ever imagined, down to the most microscopic detail? It doesn’t get much weirder than that. Now they can’t drive anywhere in L.A. without passing a Beautiful Creatures billboard, and they can’t watch TV without seeing the trailer. Chances are, you’ve seen a dozen or so commercials for the film yourself.

If you’re not already familiar with the witchy universe of the Caster Chronicles books, here’s a crash course, and we’ll keep the spoilers to a minimum. The books are set in the fictional small town of Gatlin, S.C. The protagonist is 16-year-old Ethan Wate (played in the film by Alden Ehrenreich). He’s bored, as anyone growing up in the boonies would be, and spends his days in school, playing basketball, and trying not to piss off his housekeeper, Amma (Davis). That’s until Lena Duchannes (Alice Englert) shows up.

A new girl in a place that never gets new girls, Lena is immediately declared a freak by Gatlin’s upper crust social circle, especially since her uncle, Macon Ravenwood (Irons), is the town recluse. The bullies have a point, though. Unbeknownst to them, Lena’s a caster, a fancy term for witch, and the daughter of one of the wickedest of witches (Thompson). Lena is about to turn 16, the age when casters are chosen for the light (good) or the dark (evil), and on top of that she has to deal with her raging mortal hormones. As does Ethan. They make out a bunch.

Look, just because Beautiful Creatures has the same kind of supernatural, romantic element as those books about sparkly vampires doesn’t mean it’s the stuff of cheesy lip biting and withering looks. Don’t put this in the same category as the Twilight films. Because the level of talent behind Beautiful Creatures should speak volumes. Collectively, Irons, Davis, and Thompson have three Oscar wins and four nominations between them. The film needed accomplished adult actors, because it has meaty adult roles.

“As much as our book is not like Harry Potter, I think they really wanted to follow more of a Harry Potter model,” Garcia says. “Because there are important adult roles in our book, there are adults that are as important as the teen characters, so I think that they wanted to fill those roles with really hardcore solid actors and actresses.” And she promises that the kids, Ehrenreich and Englert, aptly hold their own.

Writer/director Richard LaGravenese is no slouch himself, getting his own nomination for The Fisher King and writing screenplays for The Bridges of Madison County and Water for Elephants. Similar accolades go for the cinematographer, the costume and set designers, and other crew members. “I think it says something about the genre that big names are willing to get involved with a teen picture,” Stohl says.

LaGravenese also wrote the screenplay. As with any beloved book, fans have asked the authors if they’re worried their words will get lost in the film translation. But the women say they never wanted a direct adaptation. Besides, it’s a 600-plus page story. “I would be a terrible, terrible movie adapter … because I love to stay in heads,” Stohl says. “I don’t think economically.”

That’s why LaGravenese was perfect for the job, because he sticks to what the audience can see on the screen. The authors say he took everything in their book and pushed it as far as it could go. “It’s like bonus material. You get to see whole sections and scenes of the world in the book that we ran out of our 601 pages, and we didn’t have anymore space,” Garcia says. “I think that real fans who know the book that they go in, they’re going to be really floored when they get to see some of those things that we only touched on and that he brought to life.”

However, the two admit that they’re disappointed Charleston wasn’t chosen as the filming location. Although Garcia and Stohl live in L.A., they have crafted their books with the kind of Lowcountry fondness you’d find from someone who’s typing away in a King Street office. Chalk it up to the city’s historical preservation laws. LaGravenese went scouting with the film commission in the area, but it was impossible to do what they needed to without retreating deep within the state. Still, he toured plantations around the Ashley and took hundreds of pictures. When he started scouting in New Orleans, he knew the exact look he wanted, even if it wasn’t in South Carolina.

Overall, it’s been a surreal experience for Garcia and Stohl. But just because they’ll potentially have a blockbuster movie to their names doesn’t mean they’re forgetting about YALLFest, the young adult lit festival they’ve hosted in Charleston the last two years. They promise plenty of Beautiful Creatures swag, plus film industry panels, at upcoming events.

“Richard found us. Erwin [Stoff, producer] found us. We didn’t do any of this,” Garcia says. “They found us and put together this A-list team of people and then basically said come to the set, tell us what you think, we have fancy chairs for you, and we’re going to usher you around and treat you like the queen of England.

“It’s weird in the best way,” she adds, “but it’s weird for Margie and I because we live in L.A., and a lot of movies don’t get made and we know how lucky we are that ours is getting made.”