The Case of the Missing Servant
By Tarquin Hall
Hutchinson £12.99, 312 pages
FT Bookshop price: £10.39

Inspector Singh Investigates: A Most Peculiar Malaysian Murder
By Shamini Flint
Piatkus Original £6.99, 295 pages
FT Bookshop price: £5.59

Tail of the Blue Bird
By Nii Ayikwei Parkes
Jonathan Cape £12.99, 170 pages
FT Bookshop price: £10.39

In 1998, a professor of medical law at Edinburgh University brought out a novel that seemed to confound the laws of publishing. Alexander McCall Smith’s The No 1 Ladies’ Detective Agency was unfashionably whimsical. Its plump, middle-aged heroine, Precious Ramotswe, “Botswana’s only female detective”, spent as much time dispensing gentle wisdom as she did solving crime. Who exactly was going to buy this eccentric mix of genres? Just how many slightly sentimental, crime-friendly readers with an interest in African life could there be?

A decade later and we know the answer: a lot – and then some more. To date, The No 1 Ladies’ Detective Agency and its sequels have sold more than 20m copies in English. The original has been translated into 40 languages and was recently made into a BBC/HBO series. Meanwhile, McCall Smith has achieved more than just fame and fortune. He has inspired a whole body of imitators whose books are typically packaged with similar, cartoonishly bright “ethnic” covers that depict street markets, birds of paradise, evocatively exotic skylines and the like.

Covers apart, these books tend to share a number of characteristics. First, as with Detective Agency, there’s an aesthetic of simplicity. They tend towards linear stories, written in short chapters and short sentences. Sub-plots are straightforward; fiendish twists and nasty surprises rare.

Second, though the novels are set in the developing world, they are aimed at a western market. This often necessitates long descriptions of local customs that feel as if they’ve been culled from guide books.

Third, they all feature an investigator, who becomes involved because the police are too lazy, corrupt or incompetent to investigate properly. Inept cops are a gift for the novelist, freeing up the writer to concentrate on people rather than bureaucracy.

Fourth, though murder or abduction may be involved, the crimes investigated are typically inconsequential. There is seldom a feeling of physical danger and certainly no blood and gore.

Fifth, plots are typically resolved in favour of the virtuous. Justice is seen to be done. This runs counter to much contemporary crime fiction set in the UK or US, which increasingly revels in morally ambiguous characters.

It’s easy to understand the commercial incentive to jump on the Mma Ramotswe bandwagon. One writer who shares a publisher with McCall Smith jokingly refers to him as “Uncle”, a reference to how revenue from his books has helped support the less profitable titles on the company’s list. Several of the imitators have proved extremely successful too. But what is it about this formula that keeps readers worldwide returning for more?

It’s tempting to attribute the popularity of these novels to a desire for escapism, the literary equivalent of a package tour to a strange country in the company of a familiar guide.

But the latest crop of novels featuring crimes in foreign climes suggests readers are responding to something more subtle. Of wildly different merit, three new books all toy with the same question: what is lost when a society is forced to embrace change at breakneck speed?

Anxiety about change is a familiar feature of crime fiction, which has long drawn energy from the collision between old and new values. In the 1920s and 1930s, the air that Miss Marple and Hercule Poirot breathed was thick with angst about England’s crumbling class system, an increasingly permissive society and the slow emancipation of women in the workplace.

What has changed today is the location. When Agatha Christie’s first novel was published in 1920, a traumatised Britain was adjusting to the fall-out of the first world war. At the start of the 21st century, it’s the developing world that is convulsed by economic and technological change. By setting their stories in this environment, the new breed of detective writers is again engaging with a social revolution. These concerns are never far from the surface in Tarquin Hall’s entertaining The Case of the Missing Servant, featuring Vish Puri, “India’s most private investigator”. If Mma Ramotswe is an African Marple, Puri is an Indian Poirot: an opinionated Punjabi with an ego as great as his girth and a passion for British tailoring, malt whisky and fiery chillies.

A British journalist who divides his time between London and India, Hall combines an insider’s insight with the eclectic eye of a good foreign correspondent. The book’s plot revolves around a well-known barrister accused of killing a maidservant. But, along the way, Hall bears witness to a nation in which the wealth gap is growing and where the economic boom has done little to help the 700m Indians living on less than $2 a day.

Poverty is only part of what’s wrong, however. When we first meet Puri, he’s on the trail of one of Delhi’s degenerate youth, a spiky-haired con man lacking in “moral fibre”.

This stake-out gives Hall an excuse to lay out Puri’s moral landscape like a manifesto: “It was the same with so many young, middle-class people these days. Infidelity was rife, divorce rates were on the up, elderly parents were being abused and abandoned in old people’s homes, sons no longer understood their responsibilities to their parents or society as a whole.”

Puri’s conservative critique of his country is not just there for colour. It goes to the heart of the book. Almost everything the investigator says about family breakdown and destructive materialism in India applies also to the west. Hall encourages us to make this link ourselves but, in case we miss it, Puri is there to spell it out. “All of a sudden”, the sleuth rants. “Indians are adopting the habits of goras, white people”.

This, it seems, is the very opposite of the “exoticism” of which this kind of fiction is often accused. Instead of escaping into “another world”, western readers are encouraged to see an unflattering reflection of their own values and desires.

This trend for depicting the world’s problems in an apparently lighthearted guise is evident in another recent novel, Shamini Flint’s Inspector Singh Investigates: A Most Peculiar Malaysian Murder. The first of another proposed series set in east Asia, this time the concerns are environmental.

Singh, a scruffy Sikh with a gut to rival Vish Puri, is serving out the twilight of his inglorious career with the Singapore police force when he is dispatched to neighbouring Malaysia to investigate the murder of a timber magnate.

At first it seems that the man was killed by his wife, a Singaporean supermodel. But it soon becomes evident that the crime may have been connected to loggers in the Borneo forests, who are driving the indigenous Penan people off their land. Flint, an environmental campaigner as well as a writer, contrasts the Penan people, “never taking more than they needed”, with the “parasites in cities” who “did not understand the most fundamental tenet of nature – that a parasite eventually kills its host”. She might as well add: “And what are you going to do about it, readers?”

It is unfashionable to speak about fiction as a moral force. Yet this is exactly the claim McCall Smith makes in a recent piece in the Wall Street Journal: “Stories ... are part of our moral conversation as a society,” he said. “They change the world because they become part of our cultural history.”

And that cultural history is now a global one. Our neighbours, for whom we might assume a moral duty of care, are no longer confined to the geographically close. How can they be when every corner of the Earth is no more than a plane ride or an internet click away? Or when our collective actions, as consumers and voters, resonate thousands of miles overseas? In their modest ways, Hall and Flint are reflecting this new global village. And readers are responding in their millions.

Some writers achieve this better than others, though. For a subtler take on the new global order, Nii Ayikwei Parkes’s Tail of the Blue Bird is a beautifully written fable. Like the other books here, Parkes’s novel hinges on a clash between new and old. In this case, however, it’s not wealth and poverty that are in opposition, but reason and belief.

A bloody bundle is found in a remote Ghanaian village, but police fail to identify the remains – if indeed, they are remains. They enlist the services of Kayo, a forensics man who once worked in crime scene analysis in Britain.

The obvious path would have been for Kayo to establish the truth through technical forensic investigation. But science can only take him so far. Laboratory tests confirm that the object is of human origin but a lack of bones apparently means it can’t be a corpse.

Could there, then, be any truth to the village elder’s story about a curse on a local man who beat his wife? How to explain the flock of birds that arrives as if from nowhere when the remains are burnt, or the blue bird’s tail that appears in the hut where the bundle was found? Then again, perhaps all this talk of witchcraft merely covers up an act of rough-and-ready village justice.

As Sherlock Holmes observed, when you have eliminated the impossible, whatever remains, however improbable, must be the truth. For Kayo and his creator, Parkes, the possibility that the village elder’s talk of magic offers an explanation is left tantalisingly open.

The point of this tale is not about whether or not science works. It does: even the villagers agree. Instead, Tail of the Blue Bird is about the limits of rationalism. As conservative in its own way as The Case of the Missing Servant, this book defends a world view in which wonder and mystery, conveyed through myth and story-telling, can be considered as or more important than “truth”.

In a world where “progress” is often used as a justification for oppression, that lesson is political rather than metaphysical. As the village elder puts it: “These people: Policemen, lawyers, ministers, they will never learn; book law and gun power can never teach you how to deal with human beings. We have always had our own ways.”

As long as those ways continue to exist, this profusion of these novels, simple in form, but grappling with urgent issues, is likely to continue. But perhaps, as we launch further into the 21st century and power inevitably shifts, crime novels will again move their focus. Can it be long before we see a developing world detective investigating a crime in Britain or America? Now there’s an idea for a story.

Adrian Turpin is director of the Wigtown Book Festival