VOLKER KUTSCHER is a wildly successful German crime writer, the author of a series of dark, dangerous and – to borrow Sally Bowles’s phrase – divinely decadent bestsellers set amid the seedy splendour, appalling poverty and dubious glamour of Berlin during the Weimar Republic.

The 16-part TV adaptation of Kutscher’s atmospheric 2008 novel Babylon Berlin – at £36m it is the most expensive non-English drama series ever produced – has just premiered in Germany to rave reviews, winning the highest ratings since Game of Thrones launched. Sky Atlantic begins screening the series here on November 5 and is predicted to topple Nordic noir from its perch.

It comes as something of a surprise, however, when the 54-year-old German former newspaper editor-turned-noir novelist explains that he was inspired to go down those mean strasses, where Communists and Nazis clash, by a wonderful children’s book.

When we meet in Edinburgh after his International Book Festival event, Kutscher reveals that his favourite novelist since childhood – he was born in the Rhineland, grew up and was educated in Cologne where he still lives with his wife and their 17-year-old daughter – remains Eric Kastner, pacifist author of the much-loved classic Emil and the Detectives, first published in 1929, the year in which Babylon Berlin is set.

Kutscher’s world of brutal crime, fetishistic sex, Jazz Age drugs and corrupt politics (and in the TV version, more Charlestons than Strictly Come Dancing can shake a stick at) seems far removed from Kastner’s thrilling tale of boy sleuths. “Not at all! He’s an inspirational writer to me,” says Kutscher.

“I love Kastner’s language. It was watching the marvellous 1931 movie based on Emil and the Detectives that got me thinking about Babylon Berlin. I already knew that I wanted to write a hard-boiled American-style crime novel after watching two great movies: the American gangster drama Road to Perdition and Fritz Lang’s M Both are set in 1931. I knew that I wanted to mix those worlds, elements of Raymond Chandler and Dashiell Hammett, with the Berlin Weimar, which is also the backdrop for Emil and the Detectives, a story full of hope and optimism.

“The Weimar Republic was a well-functioning democracy for a few years before 1933 during the sometimes golden, sometimes Roaring Twenties. It really was a time of great hope. People dared to believe that the Republic could work. How that came to an end fascinates me and although there have been many novels about the Nazis and the war, there have been no German crime novels set during that Weimar Berlin period, with its strengths, weaknesses, hopes and tragic realities. Why did it fail? It’s an important question to ask because, today, we are still fighting for democracy and freedom.

“Watching the faces of those boy actors in the film of Emil and the Detectives, I kept asking myself what became of those children, guys of maybe 12, 13 years. A few years later they would go to war as soldiers. Or perhaps they went to the SS. Some may have ended up in concentration camps, others as concentration camp guards.”

It is, he continues, speaking through an interpreter, the question that haunts his novels, all of which centre on his young, fedoraed, trenchcoat-clad protagonist, the flawed, Cologne-born detective Gereon Rath played in the TV series by the charismatic Volker Bruch. Six of the novels have already been published in Germany There will be another three in the series culminating in November, 1938.

“Nine is a nice round number,” says Kutscher, acknowledging that he will be 60-years-old by the time he completes the final novel. Two of his bestsellers have been translated into English, Babylon Berlin, in which Rath investigates a porn ring and uncovers a sinister web of villainy in high and low places, and The Silent Death, about the movie industry. They are published by Scottish publisher Sandstone.

“How could a civilised country, a republic like Germany, change into this barbarous dictatorship? How could ordinary people turn into monsters?” wonders Kutscher. “I am so curious about this. It’s still incomprehensible to me, despite all the reading, all the research I have done. My plots are fictional, of course, but set against the historical background. Yes, it is a sensitive period, a shaming period to write about, but it is the lives of ordinary people that interest me. I always immerse myself in the everyday life of the times when I write. I don’t write about A-listers or celebrities, in the books, although real people do appear. When I wrote about Berlin’s film world in The Silent Death, I did not mention Marlene Dietrich. And I never write about Hitler.”

His late, maternal grandmother’s reminiscences were an inexhaustible source of material about life back then. “She was born in 1914. She grew up in the countryside but lived in Cologne as a young, Catholic housewife. She shared many, many memories. They were not actively opposing the Nazis but still they lived in fear of the Gestapo, who came and took my grandfather away on one occasion because his employer was a Jew. They were never political people but after the war they only ever voted SDP.

“I come from a very working-class family and grew up in relatively modest circumstances. My father was a sheet metal worker – hot, sweaty, dark, very, very hard work. My mother worked as an administrator but I’m the first of my family to go to university, although all I ever wanted was to become a rock star.”

He spent seven years completing his studies at Cologne University, where he read German literature, philosophy and history. “I took my time because I was also playing in a band – on keyboards – and failing to become a rock star. I still play with friends, who are middle-aged like me.” Perhaps it comes with the territory, I suggest, since Ian Rankin’s Rebus is a music obsessive while Rankin himself has a new gig, in Edinburgh, as “a dad-rock singer” performing with friends.

“Really!” exclaims Kutscher. “I'm a big fan. I love Rebus and I love Edinburgh. My detective is into American jazz.”

When rock-star fame eluded him, Kutscher was at a loss to know what to do with his degree. “I thought I might become a taxi driver: then I went into journalism and I began writing some fiction. I packed in my job and gave myself two years to get a novel published. It took 18 months to find a publisher. I actually thought no one would want to read it. Suddenly, I knew it was going to be a series ending in 1936. The books have got darker and darker, and there are so many stories to tell, so the series will end in 1938 with Kristallnacht after the big lie of Appeasement.”

What does he think of the TV version? “It’s incredibly exciting. I told the director that I was setting him free to tell the story he had to tell so long as he kept the heart and the core of my books. They have changed a lot but it’s still my story. They altered the character of Charlotte – Charly– who is a student in my book. They have made her poor and working-class, leading a double life as a prostitute. My Charly is much more petit bourgeois. But we enter completely into the world of 1929 Berlin – that is the beauty of the TV adaptation.”

“In any case,” he adds, “I have my Charly,” showing me the cover of a graphic novel, Moabit, named for the district in Berlin, telling her story in a Babylon Berlin prequel. There is also a graphic novel based on the novel. “With the TV series, I've seen three visualisations of my work this year – I think it's because I'm a descriptive writer; I create images for the reader."

There are, Kutscher admits, many pitfalls when writing fiction rooted in historical fact. “You can read my books as murder mysteries, as thrillers, as historical novels. Historical accuracy is very important to me. The facts have to be correct. When I write about real people, I always know the facts about them but I treat them as fictional characters.”

Has he ever been tempted to re-write history?

“It’s a challenge. My plots are always fictional – the historical background is set in stone. Sometimes this is unfortunate. I was writing the fifth Gereon Rath novel, set in 1933, and I really would have liked to change history as Quentin Tarantino did in his film Inglorious Basterds but it's not allowed. My job – and the fate of my fictional characters – is to follow history not change it. They can not begin to imagine what is to come – the great tragedy of German and European history, with the whole world brought to the edge of the abyss.”

Babylon Berlin and The Silent Death, by Volker Kutscher, Sandstone Press, £8.99 each. Babylon Berlin is on Sky Atlantic, November 5.