Here's why:
* Philosophical fiction: The story delves into existential themes like the nature of being, the search for meaning, and the relationship between individual and universe. The protagonist, a sperm, experiences a journey that mirrors a human's life cycle, raising questions about our purpose and the meaning of existence.
* Metafiction: The novel self-consciously examines the nature of storytelling and its limitations. Barth plays with form and narrative structure, using a sperm as a narrator to comment on the artificiality of literary creation and the constructed nature of reality.
While the novel touches on elements of science fiction (the sperm's journey is imagined within a biological context), its focus on philosophical questions and its metafictional aspects firmly place it within the realms of philosophical fiction and metafiction.