Question: The type of the novel the 2012 American coming-of-age drama film The Perks of Being a Wallflower is based on is a novel written in what form?

Context paragraphs:
The Perks of Being a Wallflower (film): The Perks of Being a Wallflower is a 2012 American coming-of-age drama film.  An adaptation of the 1999 epistolary novel of the same name, it was written and directed by the novel's author, Stephen Chbosky.  Filmed in Pittsburgh, Pennsylvania, the film was released on September 21, 2012, to positive critical response and commercial success, earning $33.4 million to a budget of $13 million.  The film stars Logan Lerman, Emma Watson and Ezra Miller.  Two or three years after the release of film, Chbosky began to speak more openly concerning the mental health care aspects of the film which were of significance to him in the original writing of the book and the production of the film as he conceived it.  This is one of the three films from John Malkovich, Lianne Halfon and Russell Smith's Mr. Mudd Productions that feature struggling teenagers; the other two are "Ghost World" and "Juno".

Moonlight (2016 film): Moonlight is a 2016 American coming-of-age drama film written and directed by Barry Jenkins, based on Tarell Alvin McCraney's unpublished semi-autobiographical play "In Moonlight Black Boys Look Blue".  It stars Trevante Rhodes, André Holland, Janelle Monáe, Ashton Sanders, Jharrel Jerome, Naomie Harris, and Mahershala Ali.

The Outsiders (film): The Outsiders is a 1983 American coming-of-age drama film directed by Francis Ford Coppola, an adaptation of the novel of the same name by S. E. Hinton.  The film was released on March 25, 1983.  Jo Ellen Misakian, a librarian at Lone Star Elementary School in Fresno, California, and her students were responsible for inspiring Coppola to make the film.

Coming Through the Rye (film): Coming Through the Rye is a 2015 American coming-of-age drama film written and directed by James Steven Sadwith.  It stars Alex Wolff and Stefania LaVie Owen as two teenagers who set out to find author J.D. Salinger, played by Chris Cooper.  The film is based on Sadwith's own quest to find Salinger.  It is Sadwith's directorial debut.

Epistolary novel: An epistolary novel is a novel written as a series of documents.  The usual form is letters, although diary entries, newspaper clippings and other documents are sometimes used.  Recently, electronic "documents" such as recordings and radio, blogs, and e-mails have also come into use.  The word "epistolary" is derived from Latin from the Greek word ἐπιστολή "epistolē", meaning a letter (see epistle).

Mud (2012 film): Mud is a 2012 American coming-of-age drama film written and directed by Jeff Nichols.  The film stars Matthew McConaughey, Tye Sheridan, Jacob Lofland, Sam Shepard, and Reese Witherspoon.  The film competed for the Palme d'Or at the 2012 Cannes Film Festival.  It was shown at the Sundance Film Festival in January 2013.  The film opened on April 26, 2013 with a limited release in select theaters, before having a wide release on May 10, 2013.  It performed well at the box office, grossing $32.6 million on a $10 million budget and received critical acclaim.

Vision Quest: Vision Quest (released in the UK and Australia as Crazy for You) is a 1985 American coming-of-age drama film starring Matthew Modine, Linda Fiorentino and Ronny Cox.  It is based on Terry Davis' novel of the same name.  Modine plays a Spokane high school wrestler who falls in love with an older woman, an aspiring artist from New Jersey on her way to San Francisco.  The film includes an appearance by Madonna, her first in a major motion picture, playing a singer at a local bar, where she performs the songs "Crazy for You" and "Gambler".  In some countries, the title of the film was changed to market on Madonna's emerging fame and the popularity of the song "Crazy for You".

Stephen Chbosky: Stephen Chbosky ( ; born January 25, 1970) is an American novelist, screenwriter, and film director best known for writing "The New York Times" bestselling coming-of-age novel "The Perks of Being a Wallflower" (1999), as well as for screenwriting and directing the film version of the same book, starring Logan Lerman, Emma Watson, and Ezra Miller.  He also wrote the screenplay for the 2005 film "Rent", and Disney's 2017 live-action adaptation of "Beauty and the Beast" alongside with Evan Spiliotopoulos and was co-creator, executive producer, and writer of the CBS television series "Jericho", which aired from 2006 to 2008.

Stand by Me (film): Stand by Me is a 1986 American coming-of-age drama film directed by Rob Reiner, and starring Wil Wheaton, River Phoenix, Corey Feldman, and Jerry O'Connell.  The film, whose plot is based on Stephen King's novella "The Body" (1982) and title is derived from Ben E. King's eponymous song, which plays over the ending credits, tells the story of four boys in a small town in Oregon who go on a hike to find the dead body of a missing child.

Boy Erased (film): Boy Erased is an upcoming American coming-of-age drama film based on Garrard Conley's memoir, titled "", with Lucas Hedges portraying Conley as a young man.  It is directed by Joel Edgerton from a screenplay that he wrote and will also produce.  The film is scheduled to be released by Focus Features on September 28, 2018.

Supporting paragraphs: The Perks of Being a Wallflower (film) Epistolary novel
Answer: a series of documents