who is the movie the devil wears prada based on
It is adapted from the novel "The Devil Wears Prada" by Lauren Weisberger. She based it on her own experience of working as a personal assistant for American "Vogue" editor Anna Wintour.
The Devil Wears Prada (novel)
The Devil Wears Prada is a 2003 novel by Lauren Weisberger about a young woman who is hired as a personal assistant to a powerful fashion magazine editor, a job that becomes nightmarish as she struggles to keep up with her boss's grueling schedule and demeaning demands. It spent six months on the "New York Times" bestseller list and became the basis for the 2006 film of the same name, starring Meryl Streep, Anne Hathaway, and Emily Blunt. The novel is considered by many to be an example of the "chick lit" genre.

Upon its publication "The Devil Wears Prada" attracted attention because of its author's background. Before writing the novel, Weisberger had worked as a personal assistant for American "Vogue" editor Anna Wintour, much like the novel's protagonist works for a powerful fashion magazine editor, who also happens to be British like Wintour. Reviewers considered the book a "roman à clef", offering insider perspectives on Wintour and other "Vogue" staff.
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The Devil Wears Prada (novel) [SEP] Introduction
The Devil Wears Prada is a 2003 novel by Lauren Weisberger about a young woman who is hired as a personal assistant to a powerful fashion magazine editor, a job that becomes nightmarish as she struggles to keep up with her boss's grueling schedule and demeaning demands. It spent six months on the "New York Times" bestseller list and became the basis for the 2006 film of the same name, starring Meryl Streep, Anne Hathaway, and Emily Blunt. The novel is considered by many to be an example of the "chick lit" genre. Upon its publication "The Devil Wears Prada" attracted attention because of its author's background.