Dwight B Wilmerding, 28 years old and saddled with a tech-support job at the pharmaceutical company Pfizer and a chronic inability to make up his mind, is offered an untested drug to make him more decisive. Since the source of the drug is a room-mate and Dwight really hates the whole indecisiveness thing, he swallows it. Being a middle-class New York intellectual, Dwight has issues in addition to his indecisiveness, but can't afford a shrink, so he undergoes psychoanalysis with Alice - his sister.

Dwight at first resists Alice's offer. If some of his problems stem from the breakdown of his parents' marriage, then his sister is hardly impartial. There's also the matter of his having entertained the odd incestuous thought. If ever someone needed to get out of town and chill, it's the hero of Benjamin Kunkel's novel.

With his girlfriend Vaneetha mistakenly forming the impression she's to be whisked off to Vermont, Dwight flies to Ecuador to meet up with his old flame Natasha, who has issued what Dwight has interpreted as an invitation to visit. Pretty much the moment his feet hit the ground, however, Natasha does a disappearing act that leaves him stranded with the prickly Brigid, Natasha's Belgian-Argentinian chum. At this point, nearly halfway into the book, we get a sense of the story beginning.

If the narrative drive of the first part is stuck in low gear, the prose itself is compelling. Like a lot of first-time novelists, Kunkel is an ambitious phrase-maker, sometimes to good effect and sometimes not. A fewtoo many observations seem superficially profound, whereas they may be profoundly superficial. Take this: "I think she guessed accurately enough what it was like to be somebody else (such as her husband or one of her kids) that the guess freaked her out and so she kept from making it". It's typical in its circular logic, a serpentine sentence that eats the tail of its own meaning.

Indecision gets much better when the action shifts to Ecuador. The narrative has more pull-through and the landscapes are vividly described. Much as we might expect a comic novel about indecision set partly in the capital of consumerism to target consumer choice, the real story here is the developing relationship between Dwight and Brigid, and how it sparks a social conscience in the former slacker. Brigid's face is "so sharp-boned and precise, but with a pleasant suggestion of former plumpness everywhere smudging it faintly with voluptuous life". As a portraitist, Kunkel writes like Rembrandt handles a brush. The tropical setting, too, inspires him: we hear "the scissoring hiss of the jungle" as if it were in our living room.

It may be considered a little old-fashioned now to be writing up druggy experiences in hallucinogenic detail, but Kunkel does it so well he gets away with it. The doors of perception are left hanging off their hinges. But wide-eyed he is not. The cruellest of ironies await those who seek chemical enhancement of the phenomenal world and, although happy endings cannot be taken for granted, the book delivers an uplifting message in dark times.

Nicholas Royle's 'Antwerp' is published by Serpent's Tail