A young man's insatiable curiosity regarding the occult leads to a disastrous magical mishap that traps him in the body of a beast. Lucius, a traveler obsessed with the forbidden arts, attempts a transformation spell that goes awry, leaving him physically transformed into an ass while retaining his human consciousness. He must navigate a world of bandits, priests, and cruel masters, enduring physical hardship and social degradation. The narrative unfolds through a series of episodic encounters, blending high-stakes adventure with biting social commentary and philosophical reflection.

Readers and critics frequently highlight the work's unique position as the only complete ancient Roman novel to survive to the present day. Discussion often centers on the seamless transition between the narrative's ribald, comedic elements and its eventual turn toward serious religious mysticism. Scholars emphasize the text's importance in the development of the picaresque genre and its influence on later European literature. The pacing is noted for its rapid, often chaotic shifts in fortune, which mirror the protagonist's own lack of control over his circumstances. Many find the balance between the protagonist's foolishness and his eventual redemption to be a compelling study of human fallibility.