In the annals of movie history, Stephen Chbosky (author and director of "The Perks of Being a Wallflower") belongs to an ultra-exclusive club of filmmakers who've adapted their own novel from page to screen.

While it's common for directors to write, produce and sometimes edit their films, even multi-talented auteurs like the Coen brothers, Paul Thomas Anderson and Quentin Tarantino have never adapted a book they wrote. Other authors-turned-directors who tackled their own material are Michael Crichton ("The Great Train Robbery") and Stephen King ("Maximum Overdrive") – neither of whom made a movie as well regarded as their books helmed by others like Steven Spielberg ("Jurassic Park") and Brian De Palma ("Carrie").

Chbosky, by comparison, has adapted his own film so well that one critic hailed "Perks" as the "next classic" of the high-school drama genre. There's even early Oscar buzz for Ezra Miller as a dark horse for Best Support Actor.

Chbosky, who published "Perks of Being a Wallflower" in 1999, reveals that there was never any doubt he would direct his coming-of-age opus. The book chronicles diary-like letters that Charlie (played by Logan Lerman) – an introverted, troubled freshman -- writes to an unknown recipient about the emotional ups and downs of his first year of high school.

His adventures include befriending an outgoing brother and sister, trying drugs for the first time and experiencing his first romantic relationship.

"It was always my lifelong dream to direct this movie, and it was so important to me, and I knew it was important to the fans that I be the one to tell the story," says Chbosky, who stressed there were no other directors he imagined would make the film.

And although it could have been considered risky to indulge an author with the opportunity, Chbosky is also an established television writer and showrunner (He executive produced the post-apocalyptic 2006 series "Jericho").

"I don't think of them as changes so much. I think of the movie of as a complement to the book, and each will lead to the other," he says.

Chbosky knew that certain aspects of the much-beloved story would have to go, not only because it's an epistolary novel but also because there was only so much of the plot he could depict in a 103-minute film.

"I had to find ways to get the audience to the same cathartic place I was able to take the reader, but it's different," Chbosky says. "In the book, Charlie can say 'Sam is so nice and pretty' and 'Patrick is so funny,' but in the movie you have to earn all of it. It can't all be from Charlie's point of view," he explains.

As a result, Chbosky says he expanded some aspects of Sam (Emma Watson) and Patrick's (Ezra Miller) characters -- they're the outgoing senior stepsiblings who take Charlie under their wing. But in exchange, he had to take out other secondary sequences that readers loved but that would have bogged down moviegoers.

"What I found in making the movie is that the stories of the extended family in Ohio or Charlie's grandfather and other subplots just didn't fit. There wasn't room!" Chbosky says.

Despite the changes, which also include narrowing down the story of Aunt Helen (Melanie Lynskey) and trimming Charlie's suicidal best friend Michael, Chbosky wants fans of the book to know there was initially a kitchen-sink draft of the adaptation that was nearly identical to the novel.

"I did the line by line version first so I could take a few months off, look at it objectively, and start to really focus the whole story," Chbosky, who started writing the screenplay in 2007, and finished his final draft in 2010, explains.

On the bright side for the book's followers, Chbosky is emphatic that he stayed true to the spirit of his characters through his casting, his exploration of Pittsburgh locations (his own hometown), and his use of music.

Although the soundtrack isn't exactly the same as Charlie's playlist in the novel, book fans will be happy to know that several of the key songs mentioned in the story – like The Smiths' "Asleep" – made it into the film.

"Picking the soundtrack was one of the biggest delights of making the movie. I would throw in my favorites from the late '80s, early '90s, and then our music supervisor would pick, and we'd go back and forth," he says. "A lot of the music made it into the movie, but there are some surprises from the era that we included too."

And as for his young cast, Chbosky says he'll always be grateful that he found such an experienced group of teen and twenty-something actors -- many of whom have been acting since they were little kids -- to play the "Perks" high schoolers.

Of the adolescent cast members, only Emma Watson was offered the part outright on the strength of her "Harry Potter" performances. "She threw herself into this part with so much professionalism and passion," he says of Watson's performance. "I know she's proud of her work on 'Harry Potter,' but she was ready to do something else, and I'm so grateful she chose our movie."

All of the other young actors, however, had to audition for Chbosky. Initially, the author-director thought he would audition Lerman for Patrick (the charismatic best friend) instead of Charlie – the quiet heart of the story.

"When Logan said he wanted to be Charlie, I was taken aback, but after he auditioned, there was no question," he recalls. "It was Logan's passion to play the part that led to it."

Chbosky says in addition to great actors, he wanted to make sure to cast "great people" who would form a tight bond on the set, and that's exactly what happened.

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Although he hosted some "getting to know you" activities (like taking them to the Pitssburgh landmarks mentioned in the book) before filming started, Chbosky says it didn't take long for the actors to become as close as their fictional counterparts.

"Most of these guys grew up on sets and around adults. Emma, Logan, Ezra and Mae Whitman – none of them had ever done things like go to the prom or necessarily walked with their graduating class," he says.

"This movie was their high school experience. They were all allowed to be kids," he adds. "They would stay up all night – and not just the four of them, all of them – and talk and play music. They had the summer of their lives."

Check out the cast of "Perks" discussing Chbosky's source material.