Billy Fisher, a young man stifled by the monotony of his provincial life, attempts to navigate his reality through a series of increasingly elaborate fabrications. Billy works as an undertaker's clerk in a dreary Yorkshire town, a position he finds deeply unsatisfying. To escape his mundane existence and the expectations of his working-class parents, he retreats into the imaginary nation of Ambrosia, where he serves as a heroic leader. His reality is further complicated by his inability to remain faithful to his three girlfriends, leading to a web of deceit that threatens to collapse at any moment. The narrative utilizes a third-person perspective to track Billy's internal dissonance as he struggles to reconcile his grandiose fantasies with his actual circumstances.

Readers and critics frequently highlight the novel as a definitive portrait of post-war British restlessness and the desire for social mobility. Discussion often centers on the protagonist's status as an anti-hero whose charm is inextricably linked to his destructive habit of lying. Many observers note the effectiveness of the author's balance between dark humor and the underlying melancholy of Billy's trapped existence. The atmosphere of the small town is consistently praised for its ability to ground the character's flights of fancy in a tangible, suffocating reality. The work remains a subject of interest for its exploration of the divide between personal identity and public performance.