Is it true that the narrator who is telling the tragic story in the movie Sunset Boulevard is dead?

Yes, it is true. The plot device in Sunset Boulevard used the dead Joseph C. "Joe" Gillis (William Holden's character) as narrator to tell everybody how his life ended under tragic comedy-drama circumstances. Specifically, in the movie, an aging silent film queen (played by Gloria Swanson) refuses to accept that her stardom has ended. She hires a young hack screenwriter, Joe Gillis, to help set up her movie comeback. The screenwriter believes he can manipulate her, but he soon finds out he is wrong. The screenwriter's ambivalence about their relationship; and, her unwillingness to let go leads to a situation of violence, madness, and death.

Praised by critics when first released, Sunset Boulevard was nominated for eleven Academy Awards and won three. It won Oscars in the following categories: Best Story and Screenplay, Best Dramatic or Comedy Score, and Best Art Direction, Black and White. It is now widely accepted as a classic, often cited as one of the greatest films of American cinema.