A lot of people seem to wonder about this because the author, You-jeong Jeong, has this unnerving way of making the psychology feel so real and specific. I checked after I finished reading because I had the same question—it just feels too uncomfortably plausible. From everything I’ve found, 'The Good Son' is a work of fiction. The setup isn’t directly based on a single documented true crime case. Jeong has said in interviews she’s fascinated by the nature of evil and the question of whether it’s born or made, which is definitely the core of the novel. She researches psychological disorders and criminal behavior to make it feel authentic, but the story of Yu-jin and his mother is her creation.
That said, the power of it is how it feels like it could be true. The domestic setting, the slow unraveling of memory, and the way violence simmers under a seemingly normal family surface—it taps into a very real, visceral fear. So while it’s not a factual account, it’s absolutely built on true psychological and emotional realities. That’s what stuck with me long after I put it down, more than any fictional thriller plot.