''It was like jumping from one frying pan straight into another,'' the 22-year-old star of the Harry Potter movies says of her new role as high school student Sam in the film adaptation of the coming-of-age novel The Perks of Being a Wallflower. ''People seem to care just as much about Sam as they do Hermione, so it was a great deal of pressure.''

The movie, based on writer-director Stephen Chbosky's 1999 bestseller, centres on the socially awkward Charlie (Logan Lerman), who seems destined to watch life from the sidelines in his first year of high school until a pair of eccentric outsiders take him under their wing. Free-spirited Sam and her fearless gay stepbrother, Patrick (Ezra Miller), shepherd him through first love, midnight screenings of The Rocky Horror Picture Show and the quest for the perfect song, which may or may not be David Bowie's Heroes.

Watson says she had no trouble relating to Sam. ''It's interesting because I think there are aspects of my growing up experience that made me also feel quite isolated, so I could definitely relate to these characters wanting to be accepted and wanting to try and find a way to fit in and feel normal,'' she says.

''Harry Potter brought me a lot of attention but that also separated me from all the normal stuff most people get to experience in high school.''

Filmmaker Chbosky - whose previous writing credits include the movie adaptation of the musical Rent and the television series Jericho - explains that he wrote the book about a similarly difficult time in his life.

''I had also reached a point where I was ready to write about why good people have to go through such bad things and how a family of friends can get you through,'' he says.

Chbosky was not afraid of Watson's Harry Potter connection. ''She grew up in the middle of a hurricane, and she did it with such grace and such class, but there is this loneliness about her,'' he says. ''I knew when I met her that this was a part of her that was just dying to come out and she just needed permission.''

The soft-spoken English actor says she hadn't read Chbosky's book before receiving the script. ''I was studying at Brown University at the time and one afternoon I picked it up and it made me cry the first time I read it, I really felt that strongly about it,'' she says.

Filming in Pittsburgh - where all three actors stayed in the same hotel - was also a coming-of-age experience for Watson: ''It felt like an accelerated adolescence because everything I had missed in my own life - from school dances and football games to sharing socks and running around together - I got to experience in a seven-week span.''

Lerman, 20, began his film career playing Mel Gibson's youngest son in The Patriot and after films such as The Three Musketeers and 3:10 to Yuma, he played the title character in Percy Jackson and the Olympians: The Lightning Thief.

''I was overwhelmed with emotion when I read the script,'' he says. ''Charlie's very naive and uncomfortable in his own skin, but he's doing his best to survive some tough situations in his past, and make it through his first year of high school.''

For Miller, the 20-year-old actor who won critical acclaim last year as the titular character responsible for a high school massacre in We Need to Talk about Kevin, this role is probably his most personal.

''I was lucky, as this weird queer kid myself, to have friends like Sam and Patrick in my own life,'' he says, ''and they put me on a regimented diet of art, including this book.

''Ironically, The Perks of Being a Wallflower became a seminal book for me in high school because it helped me understand if you can maintain your dignity in the face of pain, it will power you through the rest of your life.''

THE PERKS OF BEING A WALLFLOWER

GENRE Drama.

CRITICAL BUZZ The book has a huge following and the movie got great reviews, but small box office returns in US might hurt word of mouth.

STARS Logan Lerman, Ezra Miller, Emma Watson.

DIRECTOR Stephen Chbosky.

RATED M.

RELEASE Thursday.