Emma Donoghue’s 2010 novel “Room” tells the uncomfortably real story of a young mother and her 5-year-old son held captive in an 11-by-11-foot room. The boy narrates the book, and not only does he not understand that he and his mother are prisoners — he has no knowledge about the world beyond their four walls. The novel was a finalist for the Man Booker Prize before it even came out, and became an instant bestseller. Now Donoghue has adapted her book into a movie starring Brie Larson and Jacob Tremblay, directed by Lenny Abrahamson. “Room” is up for 4 Academy Awards — including Best Picture, Best Director, and Best Adapted Screenplay. In this extended conversation with Kurt Andersen, Abrahamson and Donoghue explain how writing this film was like working on a nature documentary — and how the right collaboration is a lot like marriage.