The success of McCall Smith's five books about Precious Ramotswe, a plump African woman who sets up Botswana's first and only detective agency, has been nothing short of phenomenal.
The series has sold five million copies in English and been translated into thirty one languages. A sixth book, In the Company of Cheerful Ladies, is published on August 23.
But next month there's another new book from this prolific author, called The Sunday Philosophy Club.
This time it is set in Edinburgh, and features a moral philosopher and amateur sleuth Isabel Dalhousie.
"She's a bit of a Jean Brodie, but a more modern version," says McCall Smith.
"Sleuths are really very useful fictional characters because all sorts of problems can come their way. They meet all sorts of people.
"It's a literary device, which I use to explore all sorts of issues of moral obligation, the limits of moral obligation, moral problems which I think people are really very interested in, in their everyday lives," explains McCall Smith.
The Sunday Philosophy Club begins with a death at the Usher Hall, a concert hall at the heart of Edinburgh's cultural life - and the city plays a central role in the book.
"Edinburgh is a marvellous character for a book," says McCall Smith. "It's such a remarkable city. It's got such atmosphere. It particularly lends itself to the haut-bourgeois noir, as opposed to other forms of noir.
"Edinburgh is a very hypocritical city. There's a veneer of politeness and underneath that, one finds an interesting story."
McCall Smith joins a long list of crime writers who have let their imaginations run riot in Scotland's capital city. Among them Ian Rankin, Quintin Jardine and Christopher Brookmyre.
Catherine Lockerbie, Director of the Edinburgh International Book Festival, says the city has always been a popular setting for crime fiction because of its split personality.
"Edinburgh's always had two sides, " she says. "It's had that very respectable, middle class, educated side and then a much darker side reflected in the actual physical structure of the city itself. The dark little closes of the old town.
"Think back to all the great Scottish writers, James Hogg, Robert Louis Stevenson - Jekyll and Hyde - of course it's a crime book.
The city has always played host to writers, whether they have dark or slightly merrier imaginations."
As he waits for the publication of The Sunday Philosophy Club, Alexander McCall Smith must hope the public's appetite for Scottish crime fiction continues unabated. But he's not taking anything for granted.
"Let's hope that the wind is fair for the book," he says. "But one has to be careful because nemesis is always stalking around and listening to us if we make remarks of that sort." (BBC)
