Emma Donoghue started writing the script for Room before the multi-award winning novel even hit the shelves.
The Irish-born author's determination to tell the "physical story" of five-year-old Jack and his 'Ma' - imprisoned in a small shed they call Room - led to last week's release of the movie's first trailer.
So far, the former UCD graduate "couldn't be happier" with the outcome.
"As soon as the book was sold at the publishers, I thought I'm going to try my hand at the script before anyone is going to be bothering me about it, while it was still private, before the book even came out," said Ms Donoghue, who comes from the Mount Merrion area of Dublin. Although there have been previous attempts, Room is the first of Ms Donoghue's books to become a film.
And the Irish-Canadian- British co-production - directed by Irish filmmaker Lenny Abrahamson (Frank, What Richard Did) - is already tipped for a slew of awards.
However, Ms Donoghue attributes this to the team's commitment, creative vision and her "endless chats with Lenny" over the kitchen table.
"Some directors thought that it would be impossible because it's partially set in just one room but Lenny was never scared of that. He always had a feeling that if you think from a child's perspective, you'll end up with something really interesting - even if for the first 45 minutes they are in a shed with a single skylight and no windows," said Ms Donoghue, who lives in Canada.
"He manages to invest that space with a lot of magic, variety and, above all, it is about the playful relationship between mother and child that makes it so watchable."
The film, featuring actress Brie Larson (Short Term 12, The Spectacular Now) and child-star Jacob Tremblay (The Smurfs 2, Somnia), will open in the United States in October. Dublin-based composer Stephen Rennicks and the RTE concert orchestra are working on the score for the film
Irish company Element Pictures was among the producers on Room, in association with the Irish Film Board.
According to the author, the film version is "very faithful" to the book - partially inspired by the case of Elisabeth Fritzl, who lived in captivity for 24 years and during that time gave birth to seven children.
"I wasn't looking to make a true crime film, I just wanted to use the imprisonment setting to explore whether the relationship between one parent and one child could be enough to make up for the lack of the world," said Ms Donoghue, who plans to return home for the Irish premiere.