Henning Mankell is pondering the recent Stockholm riots and getting just about as animated as his laid-back demeanour allows.

“I was very astonished that everyone seemed to be so astonished,” he says. “When you read the press outside of Sweden, it seemed to say this was something new, which is not true. In the last 10 years we have had riots in Stockholm, Gothenburg and Malmo, but the world press didn’t interest themselves. Everyone [in Sweden] was expecting this to happen because we have the same problem they have in London or Paris, of a small community of young children immigrants that don’t feel welcome in their own country.”

Recent political talk about tightening immigration laws are unlikely to help the situation. Maybe it’s because we think of Sweden as being a calm, rational place, but it seems out of character.

“But what did you think when Mr Breivik killed 77 children in Norway? We know that Sweden is a very decent society but there are certain problems, as there is everywhere. That mythology about the Swedish perfect society, the blonde girls and whatever, that is created by you, it’s not created by us. There is a mythology created about every country. The greedy Scotsman or some stupid thing . . . there must be something about Irish people too?”

The drunken Irish person?

“No, no,” he says with a wry smile, “if you look at television the drunk is the young British boy or girl in Ibiza.”

Despite his reputation as being a foreboding, intellectual presence, Mankell is good company, with his bone-dry sense of humour coming through his undulating Scandinavian tones. These layers should come as no surprise. While he made his name, and fortune with the Kurt Wallander series of crime novels, set in the bleak icy landscapes of northern Sweden, there's always been more than one string to his bow.

He divides his time equally between Sweden and Mozambique, where he is the artistic director of the Avenida Theatre in Maputo, and has become heavily involved in Aids awareness and literacy programmes.

In recent years, he has garnered a lot of attention for his political activism, having sailed with an aid convoy in 2010 that attempted to break Israel's embargo of Gaza, only to be stopped and boarded in international waters. He has written more than 50 plays and more than 25 non-Wallander novels, a few of which concern characters moving between Europe and Africa. Mankell's relationship with the continent goes back a long way. "I came to Africa more than 40 years ago – I'm an old man – and think I came to see the world from outside of the European egocentricity. And when I go back in August it will be for the same reason, in a way."

As romantic as that sounds, he happily admits that more practical concerns helped him find his way to the continent initially. Having left school and Sweden at the age of 16, he lived a penniless life in Paris for a time, before spending two years working as a stevedore on a ship ferrying coal to Europe and America. He returned to Sweden for long enough to write his first stage play and novel before the travel bug bit again. Why Africa? “That was the cheapest ticket I could find.”

His latest novel, A Treacherous Paradise, follows the story of Hanna Renström as she moves through a series of misadventures from a life of poverty in remote northern Sweden at the turn of the 20th century to being the owner of a brothel in Portuguese East Africa. It mixes in Mankell's own knowledge of racism, colonialism and what it is to be a stranger in a strange land.

His cheap ticket landed him in Guinea- Bissau when it was still a Portuguese colony. “On my first entrance to the African continent they stamped me into Portugal. So the madness of colonialism was the first thing I met. I’m in Africa and they say on my passport that I’m in Portugal: ridiculous.”

Leap into the unknown
Travelling to sub-Saharan Africa seems like a leap into the unknown, even for someone with experience of being a merchant seaman. The world's a smaller place now than it was in the early 1970s.

"I'm not sure. That's just what Nokia and Samsung say. With all the new technology maybe we will finally understand how big the world is – much bigger than we thought. There is so much that we don't know about other people and other cultures, that I would say the world today is not getting smaller, it's finally getting as big as it is."

Just as he has previously displayed a distaste for some of Kurt Wallander’s character traits, Mankell is quick to distance himself from the alienation felt by the character Hanna upon her arrival in Africa.

“No, that is her, she is not me. I never felt that. I think I did something right when I came to Africa: I didn’t come with suitcases full of answers, I came with suitcases full of questions. And I think this is essential if you really want to be part of a culture that is not your own. And that meant that eventually people didn’t look on me as a stranger but as one of them.”

Mankell also believes his theatre background has helped him to not be too precious when it comes to the many screen versions of his work – there have already been three different detective Wallanders, the latest being Kenneth Branagh’s for the BBC.

"You always take a risk when you say yes to a novel being turned into a film or a TV series. When Kenneth Branagh approached me some years ago I said yes, because first of all he's a very good actor, and secondly he had some very interesting ideas. The BBC have cleaned everything out [of the story] and what they've left is almost like an ancient Greek drama, and I think it's wonderful. But I can also say that maybe some of the [adaptations] haven't been as good. So what? You take a risk, and my books are always there."

While he says there is essentially only one way to tell a story – “You start with ‘once upon a time’ and you finish with the last letter” – he firmly believes that thrillers should give the brain more to ponder than just plot twists.

"The most important thing is that I can reach my reader, I'm published in 45 languages in 112 countries or something. In many of these countries I'm not looked upon as a crime fiction writer, I'm looked upon as a writer.

Democracy and justice
" All the Wallander books are basically a discussion on the relationship between democracy and the system of justice, which is one of the most important discussions we can have, because if the system of justice can't work then democracy can't work.

"People are very clever, they see the subtext of a book, they write to me and that makes me very happy, to reach these people. Call it a thriller or whatever you like, I don't care. What all the pages with Wallander have taught me is that these are important questions for people everywhere, no matter what part of the world you're from."

Perhaps splitting his time between Europe and Africa helps with communicating that message. “I think that I see the world much clearer because I have these two perspectives. Living with one foot in the sand and one foot in the snow is, to me, basic for understanding the times I’m living in.”

A Treacherous Paradise is published by Harvill Secker