The author of best-selling novel 'Room' was so confident it would be a hit movie she wrote the screenplay for it before the book was published

It can be hard for authors to get their books turned into movies, and even harder to get control of those movies once they're being made.

For every Mario Puzo who's let in Hollywood's door (author of "The Godfather" who also penned the screenplay for all three films), there's a Stephen King who isn't (he's publicly bashed most of the adaptations of his work).

And though the J.K. Rowlings, Stephenie Meyers, and E.L. James' of the world have had a lot of power in shaping their pages to screen in the last few decades, recently the movie world has opened the door even wider for input from authors in the adaptation process.

Author Stephen Chbosky adapted his own novel "The Perks of Being a Wallflower" (he also directed the film), Gillian Flynn wrote the book "Gone Girl" and the screenplay (which earned her a Golden Globe nomination for Best Screenplay), and now there's Emma Donoghue.

The Irish-Canadian has written eight novels, but the adaptation of her 2010 New York Times Best-Selling book "Room" is the one that has now given her cross-over appeal as it has become one of the most buzzed about films this awards season.

But what sets Donoghue apart from many other author/screenwriters is that Donoghue wrote the screenplay for "Room" before the book was even published.

"I didn't want to have some company come along and say 'Let us take it off your hands and have some experienced writer take it,'" Donoghue told Business Insider. "I decided that, privately, I'd do a draft of it myself before anyone could tell me what to do."

Donoghue had experienced the more traditional path with her previous books - a production company hiried on a screenwriter to adapt her stories.

But those movies never got off the ground.

The author had such a good feeling about "Room"'s cinematic prospect, she wanted to be ahead of the game this time.

"And I wanted to be honest," said Donoghue. "If I found the right filmmaker I wanted to be able to say, 'Look, I'm not trying to force you to hire me, here's my script, can we work together?'"

But Donoghue also admitted that if her book were to be made into a movie she wanted to try her best to keep it as true to what she created.

"Room" is an emotional tale filled with as much tension as warmth. It follows a 5-year-old boy and his mother as they are held captive in a small shed. But a big stand-out about the book is it's told in the voice of the 5-year-old, Jack. The only glimpse we get of his mother, which he calls Ma, is from Jack's point-of-view.

Certainly not an easy task to adapt into a movie for the author of the book, let alone a screenwriter.

But Donoghue said she wasn't afraid to rework the story so it was more cinematic. She took out a lot of the social commentary that's in the second half of the book, as well as an incident where Ma had a stillbirth before Jack was born.

"You always have to streamline," she said about writing a screenplay. "I'm not left with any regrets."

While taking meetings with numerous filmmakers who wanted to make the film, which included established names, she was given a ten-page hand-written letter from a fellow Irishman, independent filmmaker Lenny Abrahamson.

"I had a big emotional reaction to the novel, being a parent with a young boy at that point," Abrahamson told Business Insider. "I had very strong images of how this novel should be adapted and what not to do and what to do. So the letter to Emma was, 'I know it, I know how your novel works. I promise I won't f--k it up.'"

Donoghue instantly felt that Abrahamson got the book and got what she was doing.

"He immediately got my references to Plato in the book," she explained. "He understood this was both a realistic story about people being kidnapped and a metaphor for the moment when you move from childhood into adulthood. And he didn't call it The Room."

Once Abrahamson realized that Donoghue had a script he embraced her involvement. In fact, he pushed her to keep things in the script from the book that she was reluctant to include.

"One thing I changed immediately for my first draft of the script was Jack's long hair," said Donoghue, who felt that looking at a boy's hair that goes down below his shoulders in a movie would have looked bizarre.

"But Lenny said, 'No, go back to the long hair.' He was just unafraid of the unconventional aspects of the screenplay."

Donoghue and Abrahamson worked on the script together for months. Flying back and forth to each other's home, with almost no interference from the film's backers. They fleshed out Ma so the character in the film would be a stronger presence than in the book while still keeping Jack as the foundation for the story.

The finished product is an emotional, tear-jerking ride that is excels with Abrahamson's direction and Oscar-worthy performances by actress Brie Larson as Ma and newcomer Jacob Tremblay as Jack.

The film won the Audience Award at the Toronto International Film Festival. Winners of the prize often go on to receive a Best Picture Oscar nomination.

For Donoghue, seeing the film was a thrill, especially watching Larson as Ma.

"Ma was a very real character in my mind but for the book I had this frustrating fact that she was just through Jack," she said. "So seeing her on screen was beautiful. She's strong, and motherly."

Donoghue knows that the experience she had with Abrahamson making "Room" is extremely rare. And though she wants to continue writing screenplays, so knows she'll likely never have that kind of bond and understanding with a director again (although they both say they want to work with each other moving forward).

"The whole thing was made protectively," she said. "It's like the little room."

"Room" opens in limited release on Friday.