The opening of Iain Reid’s 2016 psychological thriller, I’m Thinking of Ending Things, is straightforward enough: An unnamed young woman goes on a road trip with her boyfriend, Jake, to visit his parents, who live on the farm where he grew up. She’s thinking seriously about breaking up with him; although they have a real connection, there’s something about their relationship doesn’t feel quite right to her. For one thing, she can’t quite remember how long they been dating—it’s something like seven weeks, she thinks, but she’s not sure.

Her feelings of uncertainty and anxiety grow as Jake and the young woman have long, philosophical discussions about life and death, and share odd stories from their pasts. Things get more unsettling as the novel goes on: At the farm, Jake tells a story about maggot-eaten hogs, shortly after she sees two dead, frozen lambs; during dinner, Jake’s mentally ill mother won’t stop grinning, even as she tells the young woman about the voices in her head; and the young woman realizes she’s been unknowingly biting her own fingernails to point of bleeding—and a piece of nail is lodged in her back teeth. On the way home, Jake and the young woman go to a very off-putting Dairy Queen and then make a stop at an empty high school, where a janitor appears to stalk the woman.

Throughout the novel, there are occasional snippets of cryptic conversation between two unidentified people; they seems to be talking about a crime of some sort. A revelation near the end—one that brings to mind Fight Club, if that book had been written by a philosophy major—mostly clarifies what’s going on and recasts the story as a giant puzzle. Indeed, one would think that this twist would make this Kirkus-starred novel nearly unfilmable, but writer/director Charlie Kaufman decided to take up the challenge anyway—with mixed results. His new Netflix film premieres Sept. 4 and stars Chernobyl’s Jessie Buckley as the young woman and Friday Night Lights’ Jesse Plemons as Jake.

Kaufman is a novelist himself—his debut, Antkind, was published in July—and he’s no stranger to odd narrative structures. He wrote the metafictional screenplay to 2002’s Adaptation, which combines Susan Orlean’s nonfiction book The Orchid Thief with a fictional tale of Kaufman and his twin brother writing a script based on Orlean’s book. So perhaps it’s not too surprising that Kaufman, in his adaptation of I’m Thinking of Ending Things, thinks of changing things. His film is mostly faithful to Reid’s book, but there are differences—and they’re not small ones.

For example, at Jake’s parents’ house, the young woman experiences strange time jumps, during which she meet Jake’s parents in the past, when they were relatively carefree, and in the future, when they’re wracked by old age and dementia. These are powerful scenes, and they provide opportunities for Toni Collette and David Thewlis, as Jake’s parents, to show off their considerable acting chops. From then on, the film spirals into a weird fever dream that culminates in an extended dance number and a stage rendition of the song “Lonely Room” from the musical Oklahoma!. None of this appears in Reid’s novel, which takes its time in going off the rails.

Kaufman also introduces numerous references to books and authors, including David Foster Wallace’s 1997 essay collection, A Supposedly Fun Thing I’ll Never Do Again, and Anna Kavan’s 1967 SF novel, Ice. The young woman also delivers a bizarre, Pauline Kael–ish film-criticism screed about a John Cassavetes movie.

These are pretty significant alterations, to be sure, and they would be unforgivable in most other contexts. But, oddly enough, they don’t cancel out the book’s central secret—they just take it in new, and very strange, directions. The problem is that Kaufman buries that secret under so many layers of surreality that one could easily miss it—that is, if one hasn’t already read the book. It’s a puzzling choice on Kaufman’s part, but maybe it’s appropriate one for what is, in the end, a puzzle-box of a novel.

David Rapp is the senior Indie editor.