Daniel, By Henning Mankell, trs Steven T Murray

An orphan of the Kalahari feels ill at ease in Sweden

Fainting at the prospect of dissecting a whore's corpse rules out a career in medicine for 27-year-old Hans Bengler. Casting around for a purpose beyond his comfortable weekly appointment with Matilda, his favourite prostitute, Bengler settles somewhat whimsically on entomology and begins nursing an ambition to discover an insect that he can name after himself. He takes leave of his moribund father, pillages the family estate for a meagre haul of floggable silver, and sails to Africa.

Cape Town in the late 1870s has few delights, and Bengler hastily strikes out for the Kalahari desert. His ordeal – managing porters, theft, desertion, calamity and near death – causes Bengler to justify this eccentric enterprise to himself. Questioning his sun-blasted wits and madcap ambition, his commentary has a hallucinatory quality that makes for one of the more compelling episodes in this interesting but uneven novel – if only because Bengler's character is not one of heroic endeavour but of stubborn adherence to ill-conceived plans. Impetuous and slightly pathetic, Bengler is in flight from his own cumulative drift and failure. His erratic interests and appetites are the main drivers of a narrative that would make an engaging picaresque if his personality possessed a bit more vim, conflict or introspection.

It's hard to judge whether the author wanted to portray a rather bland character, or whether Bengler suffers more from the author's occasional blunt phrasing of his interior monologues. Take this rumination: "'I'm searching for an unknown fly,' he thought. 'The way other people search for a god.'" There's little scope here for ventilating deep anxieties or existential aspiration. A similar stolidity of mind afflicted the protagonist of Depths, Mankell's 2006 novel of maritime espionage during the Great War, which was billed as a psychological thriller but proved somewhat light on both psychology and suspense.

When presented with a native boy, traumatised and orphaned by the indiscriminate slaughter by white hunters, Bengler makes a snap decision to adopt. Dragging the boy (sometimes literally) back to a civilising regime in Sweden becomes Bengler's grand plan, and the substance of this novel. "My name is Daniel. I believe in God" is drilled into the boy who, despite Bengler's nobler scientific intentions, inevitably becomes another specimen to be showcased and discussed, alongside his adoptive father's travelling cases of pinned and labelled insects.

If Bengler proves obtuse, Daniel's voice presents a different challenge. Mourning and dislocation encourage muteness. Daniel's childish grasp of the world is anchored in the song and scorch of the Kalahari sands, so he is bewildered by Scandinavia's climate and landscape and distressed by the spiritual sundering from his native beliefs. His response is a mixture of uncomprehending obedience, and a powerful undertow of yearning for return, which gives the novel its presiding mournful tone. Even with Daniel's unconvincingly swift apprehension of rudimentary Swedish, Mankell's options for articulating the nature of the boy's hurt are limited.

One puzzle is why Mankell's Wallender series of police procedurals are so good – gritty and nuanced, with vital characters and driven plot – while some of his other fictions flounder. There's an understated theme of cultural and racial insensitivity in Daniel that Mankell, from his robust personal engagement with communities in East Africa (he lives in Mozambique for six months of the year) is well equipped to tease out but doesn't, despite his proven skill at levering bold themes such as cyber-terrorism or resurgent neo-Nazism into his thrillers. As a fiction, Daniel makes an intriguing historical vignette, but the principal characters' under-probed psychologies and the dwindling narrative pace give the reader too little purchase to hold on to any more significant meaning.