Will Self has a habit of embarking on ambitious fictional journeys he doesn't know how to complete. His American protagonist, Tom Brodzinski, shares his predicament. While holidaying on a sun-baked island continent, Tom inadvertently throws a cigarette-end onto the head of a local man. This small act involves him in the toils of an increasingly complicated legal system. Travelling inland with a paedophile Englishman, he meets untrustworthy officials, wacky sorcerers, aloof tribesmen and violent insurgents. Intended parallels with the Iraq war are unmistakable but remain confused.

Self's distinctive vocabulary is part of the problem. Where there should be nuance or discrimination, he proffers a bower-bird display of brash bits and pieces. Gaudy Greek and Latin derivatives do nothing that their simpler synonyms couldn't do as well. “Lenticular” clouds are then said to resemble lenses - well, that's what “lenticular” means. “Hispid and viscid” recur to describe a fly's legs but are superfluous. “Gravelly” portrays the sound of ice-chips in a drink and the burbling of a moa. The double application halves its graphic force.

The book also suffers from the overproduction of simile and metaphor. A “hypodermic spire” appears twice, while crude Freudian images turn up everywhere - a cigar is a “vegetative glans”, a cigarette becomes a “miniature white penis”, an automatic rifle is “curved up like a penis”. The self-conscious stylistic elaboration works against readers' acceptance of the strangeness of the story, so when we are told that Tom “had blundered into a psychic quagmire” we are unconvinced.

Lurking below the surface are important questions - what connections are there between ethical intentions and outcomes, can we be held responsible for accidents, do we have the right to impose our idea of good on others? They fail to emerge, however, as they're overwhelmed by trivial interventions from the author, gratuitous pieces of Grand Guignol and a mishmash of anthropology and zoology. The plot zigzags luridly to no purpose - a consul kisses Tom with his “wet and plump” lips; two hunters have “rambunctious” sex wearing giant baby clothes.

Sometimes the writing is effective. There's a sharp portrait of a settlement with its landscape of “shit, trash and broken glass” and pus-eyed children. But what might have been an ironic account of modern liberalism becomes something more cosy. Tom's travelling companion is the kind of imaginary Brit who talks of “that bally juju” and “my lady wife”, and is obsessed by cricket scores. Lampooning long-dead clichés is more sixth form than Swiftian. A book that sets out to be dangerous and adventurous is contained safely within the apparently limitless boundaries of its author's self-indulgence.

The Butt by Will Self
Bloomsbury £14.99 pp368

Explore Books

• Book Extracts

• Book Reviews

• Books Group

Times Recommends

• Avro Lancaster: Owner's Workshop Manual
• iD: The Quest for Identity in the 21st Century by Susan Greenfield
• Fatal Misconception by Matthew Connelly