Stephen Chbosky’s new film, The Perks of Being a Wallflower, is set in the 1990s and highlighted with pop culture touchstones of the time (think mix tapes and Morrissey posters). There’s not a cellphone in sight. But don’t think of the movie, which opened Friday, as a period piece.

“I wanted the film to find every bit of style that is timeless,” says Wallflower writer-director Chbosky, who based the film on his popular young adult novel about friendship, overcoming the past and growing up. “If it was just the ’90s, I wasn’t interested. … If we talk about our first kiss we had in school, in our memory our hair doesn’t look bad. We’re not wearing strange sweaters. I wanted the film to look like the emotion of the film — that’s what would make it timeless. Adolescence is eternal. This time of life will always be the same, even though now there’s Twitter and Facebook.”

Thousands of teens who have read and loved the modern classic about shy, troubled 10th-grader Charlie, whose life lights up when he’s befriended by senior stepsiblings Patrick and Sam, would likely agree that Wallflower’s appeal is universal. And to those fans, Chbosky, 32, is unfailingly loyal. Not every author gets the chance to make the movie version of his book, but Chbosky, who also wrote the screenplay for Rent and is one of the creators of the short-lived but underrated TV series Jericho, fought hard for the opportunity.

“The fans of the book are so passionate, I couldn’t risk it in the Hollywood machine,” he says. “It was the most challenging screenplay I’ve ever written, just by the nature of what the book was — a first-person epistolary novel. To turn that into something objective with the same emotional intimacy and emotional catharsis was hard.”

The first actor to sign on was a coup for the film: Emma Watson, fresh from her stint as Hermione Granger in the Harry Potter series.

“Emma and I were kindred spirits,” Chbosky says. “We met in New York City, and I saw this wonderful, vulnerable, somewhat lonely girl who grew up in the eye of a hurricane and was desperate to do other work to prove to herself she could do it. She was the perfect Sam. I built the cast around her.”

From there Chbosky settled on Ezra Miller ( We Need to Talk About Kevin) as the playful Patrick and veteran Logan Lerman ( Percy Jackson & the Olympians, Hoot, 3:10 to Yuma) in the pivotal role as Charlie. Also cast were Dylan McDermott and Kate Walsh as Charlie’s parents and Nina Dobrev of The Vampire Diaries as his loving but distracted older sister.

Lerman says he thought he was perfect for the role, but he knew he’d find himself challenged because so much of Charlie’s turmoil is internal: “It’s a pretty tough arc to figure out. Trying to manage the tone of the whole film while shooting it out of order was a little tough, too.” What helped him? Having a great source walking around on set.

“Stephen’s writing is really compelling,” Lerman says. “He knows every little detail about each one of the characters. He was incredibly insightful. He was like having a cheat sheet for the project; I could go to him and ask him anything. It was just a luxury to have him around.”

“Logan’s a very serious young actor,” Chbosky says. “He does his homework … it wasn’t me dictating to him. It was him seeking me out, and we became great friends through so many discussions. I even took him to my parents’ house for chicken paprikash. He loved it.”