After having seen the film twice, I decided to read The Perks of Being a Wallflower by Stephen Chboski. Originally published in 1999, I was amazed the slender work could be adapted into a two hour film.
The novel (novella?) consists of a series of letters written by Charlie, the protagonist, to an unknown "friend" over the course of one school year. It is explicitly set in the 1991-92 academic year. The film starts with this epistolary plot device but abandons it until picking it back up for the epilogue. In the book, the effect of the letters is to make fuzzy what was presented as facts in the film. Since Charlie's subjective observations are the topic of his letters, the reader is left to wonder about his biases and as the novel continues, his mental state. The film presents the events written about in Charlie's letters as gospel but there is some ambiguity in the novel.
Charlie's relationship with his sister is much deeper in the novel. In the film, Ponytail Derek slaps her and Charlie keeps quiet. She eventually dumps Derek and goes to the prom alone. In the novel, Charlie reports the incident to his English teacher (Paul Rudd) who reports it to Charlie's parents. This forces her to keep her relationship with Derek a secret because her parents insist she have nothing to do with him. She continues to see him secretly (even having a "fake" boyfriend) and eventually becomes pregnant. She tells Charlie who drives her to the abortion clinic. This remains their secret throughout the novel. She dumps Ponytail Derek (the character has no name in the book) because he denied being the father of the baby and has a new boyfriend by the time of the prom.
The tone of the novel is much darker than the film. Charlie witnesses a rape and the dysfunctional family dynamics on both his maternal & paternal sides are explored through holiday visits and recounted stories. Charlie's family has been through a lot going back at least two generations which legitimizes his illness and the concerns of his family. Charlie is seeing a psychiatrist for most of the book whereas he only sees one after his nervous breakdown the film.
Oddly, the character of Mary Elizabeth goes to Cal Berkeley in the book instead of Harvard in the film. There are other small discrepancies but the biggest difference was the humor or lack thereof. I thought the film had moments of inspired comedy whereas the book focused more on Charlie's sadness and difficulties.
I've read that The Perks of Being a Wallflower is a cult favorite among a certain segment of the population. I can understand that. It reminded me a little of Catcher in the Rye by J.D. Salinger. If I had to provide a pithy quote, I'd say The Perks of Being a Wallflower is the MTV generation's Catcher in the Rye. The odd thing about the film is the time it took to adapt the novel. The "MTV generation" is in the 30s or even 40s now. My quote isn't nearly as original as it may sound. The Perks of Being a Wallflower was originally published MTV Books which I believe has been bought out by Simon & Schuster.