Why does Yunior narrate the story about the Cabrals, what investment does he have in it? Silence dominates the novel, what are his silences?In page...

There are really three narrators in Diaz's novel: the old Yunior ("The Watcher"), Lola, and the young Yunior.  The old Yunior narrates most of the novel.  He's the one with all the footnotes.  Near the end of the novel, he calls himself "The Watcher" because he is an outsider (not in the Cabral family).

The novel must be narrated by an outsider, someone who's lived with Oscar and dated Lola, someone who's made since of this story over time, someone unaffected by Trujillo.  Yunior is very much like Junot Diaz himself: good-looking, confident, a closet nerd.  In only a short time, Yunior was forever changed by Oscar.  More importantly, he's lived to tell the tale; he's not been cursed.

The second chapter is narrated by Lola, her only narration.  Much like Addie's only narration in As I Lay Dying, the female voice is buried in this patriarchal culture.

The young Yunior only narrates the college chapters.  He doesn't footnote as much.  He's full of machismo and curses a lot.  He's got sex on the brain.  We can tell he doesn't like Oscar all that much.  Although the college chapters appear near the middle of the novel, they seem to have been written first.

Oscar's tragedy obviously affects the immature Yunior, to the point that he wants to finish what Oscar attempted--to be a writer and teacher.  Maybe he's not the next Tolkien, like Oscar wanted to be, but Yunior deftly blends all the voices into a post-modern collage of fantasy, tragedy, comedy, romance, and myth.