Actress Julia Roberts devoured R.J. Palacio's debut novel, Wonder, over a single weekend, reading it aloud with her three children. The following week, she called her agent.

"I read it with my kids, they all loved it and I thought, this has to be made into a movie," she says.

The story tells of August Pullman, a boy born with facial differences who is home-schooled until, at the age of 10, he enters mainstream education and has to cope with the pressures of interacting with other children, facing a world of gawking kids who do not yet know how to face him back.

The novel was a publishing phenomenon, quickly earning five million sales on its way to the top of the New York Times bestseller list, and when Roberts expressed interest in starring as August's mother, its journey to the screen gained pace.

It is a heart-warming story that explores what it means to be different and Roberts believes the film might offer hope to children who feel like outsiders or are bullied at school.

"It is such a complicated topic," says the Oscar-winning actress, "and having children myself, I think this novel was a great conversation piece for us as a family. And the one thing I can truly, truly hope and that I think is attainable is for anyone who is feeling picked on or bullied is to have a voice to some adult and not to keep it to themselves.

"That is the first step towards solving it, sorting it and understanding it and being able to heal and move on from it."

The film is directed by Stephen Chbosky, who wrote and directed The Perks Of Being A Wallflower (2012), while the main character is brought to life on-screen by young actor Jacob Tremblay, who wore heavy prosthetics throughout filming.

For Palacio, it was imperative the film-makers did not shy away from August's craniofacial differences.

"I didn't want a movie that would minimise the severity of Auggie's facial differences because that's such an important aspect of who he is," she says.

During her first discussions with film-makers, some producers spoke about not showing August at all, a move she found utterly repellent. "It was very important for me to make sure the audience sees Auggie front and centre from the very beginning," she says.

She was inspired to write the novel following a moment around 10 years ago, when she was sitting in an ice cream store with her two sons.

"My younger son was very young, only about three years old, and some people sat down next to us with a little girl," she recalls.

"The little girl looked just like Auggie does in the book; she had a very, very severe facial difference and my little boy reacted and started to cry a little. She was hurt from seeing his reaction. And in my haste to shield her from his reaction, I whisked him away."

She says she immediately regretted her actions. "I could not stop thinking about all the better ways I could have handled that situation. I should have turned to the little girl and started a conversation. There were a million things I could have done differently and I became obsessed with that scene and thought, I am going to write a book about what it is like to face a world every day that doesn't know how to face you back."

She determined that her central character was likely born with Treacher Collins syndrome which, though caused by a mutation in just a single gene, can result in a radically altered formation of the bones in the face.

The book was embraced by many of those with craniofacial anomalies and the film-makers worked closely with that community during production.

Indeed, Roberts says she found these families very inspiring. "I think all families are special and some have incredibly focused people in the family to take care of; I can't imagine what's that like.

"We have made our attempts and created this story about it, but all families will do the best they can with what they know. I think it's important to love one another as deeply as you can every day because you know the days are short."