Junot Diaz’s first novel (following Drown, his acclaimed book of short stories) sets out its stall right at the beginning: “Our hero was not one of those Dominican cats everybody’s always going on about – he wasn’t no home-run hitter or a fly bachatero, not a playboy with a million hots on his jock.” Oscar is an overweight nerd who, growing up in New Jersey in the 1980s, defies stereotypes about immigrants from Central America by being into activities more usually associated with spotty white kids from the suburbs – science fiction and role-playing fantasy games.

Much of the first part of the novel is concerned with establishing and playing extended riffs on this disjunction, as well as introducing us to a bloody historical back story – the brutal dictatorship of Rafael Trujillo that blighted the Dominican Republic between 1930 and 1961. These preliminaries involve thickets of references to characters from science-fiction comics and slabs of Dominican history, to the extent that context threatens to suffocate the narrative. This feeling of constriction at times takes on a typographical aspect, as Diaz’s long footnotes squeeze the main text to a few lines at the top of the page.

This is one of those novels that starts falteringly, then picks up a momentum that sweeps us through to the end. The opening sections, which introduce us to Oscar and his feisty sister Lola, have the overfamiliar feel of many other American coming-of-age narratives on page and screen (albeit here with a Hispanic accent), populated by a central-casting lineup of jocks, geeks and frustrated sexual urges. The tipping point comes when Diaz leaves American shores and takes us back to the Caribbean and into the past. Oscar and Lola’s mother, Beli, has hitherto appeared only as a tyrannical presence in their lives. Now we learn the history behind her hardness – a horribly engrossing tale of sexual exploitation, careless violence and sheer bad luck (which lay, above all, in falling in love with a man known as the Gangster; what she didn’t know when she became pregnant by him was that he was already married, to one of Trujillo’s sisters). She only just escaped with her life.

But that was not the beginning of the family’s misfortunes. Diaz’s narrative weaves further back, to the 1940s. The most powerful part of the book tells the story of Oscar and Lola’s grandfather, a doctor who survived by keeping his head down and not asking questions while so many around him were being wiped out. But even he was not immune when Trujillo’s infamous sexual appetites appeared to home in on his daughter. In slow motion, we witness an ordinary, unheroic man’s carefully constructed world fall apart.

Diaz evokes the nightmarish reality of living under a total and arbitrary power with a dark irony reminiscent of central European writers such as Milan Kundera.

But the greatest risk he takes comes when he narrates the sad end of Oscar himself – and suggests that the curse, the fuku, that has afflicted his family has outlived even Trujillo. Oscar is a Holy Innocent, a familiar literary type, and his self-martyrdom on the altar of an idealised love could easily have descended into bathos and sentimentality. By a triumphant whisker, Diaz avoids this – and creates a memorable end to a novel that had started unpromisingly.

The Brief Wondrous Life of Oscar Wao by Junot Diaz
Faber £12.99 pp340

Available at the Sunday Times Books First price of £11.69 (inc p&p) on 0870 165 8585

Times Recommends

• The Sunday Times 100 best holiday reads
• What will we be reading this summer: the booksellers predict
• Literary festivals: a survivor’s guide