The novel is about the complex friendship and relationship between two teenagers, Connell and Marianne, who both attend the same secondary school in County Sligo, and later Trinity College Dublin. It is set during the 2000s downturn period. In the book's story, Connell is a popular, handsome, and highly intelligent high schooler who begins a relationship with unpopular, intimidating, and intelligent Marianne, whose parents employ his mother as a cleaner. Connell keeps the affair a secret from school friends out of shame, but ends up attending Trinity alongside her after the summer and reconciling. Well-off Marianne blossoms at university, becoming pretty and popular, while Connell struggles to fit in properly for the first time in his life. The pair weave in and out of each other's lives across their university years, developing an intense bond that brings to light the traumas and insecurities that make them both who they are.