Here is the Wikipedia description of the book:
... the "brief wondrous life of Oscar Wao," an overweight Dominican boy growing up in Paterson, New Jersey and obsessed with science fiction and fantasy novels, with comic books and role-playing games and with falling in love, (and) also the curse of the "fukú" that has plagued Oscar's family for generations and the Caribbean (and perhaps the entire world) since colonization and slavery.
The middle sections of the novel center on the lives of Oscar's runaway sister Lola and his mother Hypatia "Belicia" Cabral and his grandfather Abelard under the dictatorship of Rafael Trujillo. Rife with footnotes, science fiction and fantasy references, comic book analogies, various Spanish dialects and hip-hop inflected urban English, the novel is also a meditation on story-telling, Dominican diaspora and identity, masculinity, the contours of authoritarian power and the long horrifying history of slavery in the New World.
Yes, it's all that. It's terribly well written, and very moving. The language is very powerful. It was good to hear it read by the author who swapped with great ease between different languages and forms.
Oscar Wao is rather like the youngster in Watchmen who is reading 'Tales of the Black Freighter', and indeed in the last couple of paragraphs of the book Diaz quotes Doctor Manhatten, which was satisfying. But the whole thing is very rich, and it draws its imagery from a wide spread of genres, including SF fantasy, role play games, comics, etc.