Emma Donoghue's 2010 novel Room, a surprisingly hopeful work about a woman and her 5-year-old son being held captive in a garden shed, became a surprise bestseller. The book, which is now the basis of a new film generating Oscar buzz, allowed the Irish-Canadian author to earn her first screenwriting credit. The Hollywood gig, as she explained to PW, turned out to be nearly two decades in the making.

It’s fairly unusual for an author to write the screenplay for the movie adaptation of their book. How'd you land the job?

As soon as I sold the novel, I thought about how the story might work on screen, so I went ahead and drafted a screenplay. That might seem presumptuous, but it was actually motivated by a sort of modesty. I wanted to be able to say to filmmakers: 'I'm not asking you to hire me just because I wrote the novel, but do look at this screenplay and decide if you can work with it.' Then, after the book was published, I heard from a bunch of producers, directors, and actors. I never felt the right spark, until I got a 10-page letter from an Irish director, Lenny Abrahamson. We wound up striking an unusual deal, in that we agreed to develop the project together over several years, rather than my selling the rights. I now understand this is really unusual for the writer, and I've enjoyed every minute of it.

Before penning the screenplay for Room, had you done any screenwriting?

I did have some experience. I was hired 20 years ago to adapt my first novel, Stir-Fry. But, after many drafts, our funding fell through. I've also tried my hand at one original screenplay. So I wasn’t afraid of the format, I just hadn’t had any success. In the case of Room, I had an instinct that this story—and its child’s perspective—could work well on screen, so it seemed natural to me to try writing it without waiting for anyone to hire me. I also wanted to do it before filmmakers might come along and suggest other, more experienced screenwriters for the task.

Do you have any formal training in screenwriting?

I have no formal training in any kind of writing. The concept of studying creative writing came late to the British Isles; our tradition is, stay in your room reading and writing till you come up with something good. I’ve written in many forms, including stage and radio plays which were probably the best preparation for scriptwriting because, unlike fiction, they're time-based drama, meaning that you have to stay aware of the risk of the audience beginning to shift in their seats. But I’d love to write for the small as well as big screen, either original projects, adaptations of my work or of other people’s.

What were the biggest changes you made to the story in the screenplay?

Translating the first-person narration into action and reaction from Jack, rather than relying on voice-over, was a challenge. I did add some voice-over to the script at a late stage, at Lenny’s request, but more to mark the different sequences than for information. Ultimately I tried to make the story into more of a two-hander than the novel. The goal was to satisfy all those readers who’ve written to me begging for “more about Ma.”

This interview has been edited and condensed.