Here's why:
* Focus on Personal Narrative: The book heavily relies on Jeannette Walls' personal experiences and her coming-of-age story, a defining characteristic of postmodern literature.
* Unreliable Narrator: Walls' account is subjective, influenced by her childhood experiences and her perspective as an adult. This fits the postmodern concept of questioning traditional narrative authority.
* Fractured Narrative: The story isn't told in a strictly linear fashion, jumping between different time periods and perspectives. This fragmented narrative structure is common in postmodern works.
* Social and Political Commentary: The book tackles issues like poverty, social mobility, family dynamics, and the American Dream, often with a critical lens typical of postmodernism.
While "The Glass Castle" touches upon elements of other periods like realism and confessional writing, its core thematic and stylistic elements align most strongly with postmodernism.