An infectious magical-realist yarn about petty thieves and lost children in modern-day Venice, The Thief Lord is illustrated by Funke herself and contains glimmers of the darker obsessions that motivate her outside the written realm. The novel’s success has also unleashed a backlog of her German-language work, freshly translated for the huge and hungry Potter constituency. Books such as Inkheart, a terrific self-deconstructing fable about the power of books themselves, and Dragonrider, a modern twist on fire-breathing folklore, are now being passed from child to child. This, Funke claims, is the only marketing technique that matters.

“In the long run it has to be word of mouth,” says Funke, a lean and elegant 45-year-old with smiling eyes. “Nothing else works. If there’s some media interest but the children don’t like the book, they just throw it out. That’s the good thing about children — you can’t fool them with a name or a Wall Street Journal article. So therefore I’m quite proud of that, that it always happens that the children tell other children.”

Funke is the latest in a long line of authors to be tipped by an ever hopeful publishing industry as Rowling’s natural heir. In this case, however, comparisons run deeper than merely working in the same genre. She shares a British publisher with Rowling, for one. She also made a similar late-blooming transformation from relative obscurity to worldwide sales in the millions, and is now set to follow Rowling to big-screen success.

“Everybody says: the German J.K. — do you mind?” Funke smiles. “I don’t mind, because at the moment it’s obviously the choice they pick. A few years ago they would have said someone else. It’s just a teaser, shorthand. But we have the same publisher, Barry Cunningham, and the same woman who accompanied her on her American tour also accompanies me.

“I love J. K. Rowling’s interviews, they are so well done. What I’m really impressed by, for example, is the way she deals with torture in a children’s book. I am always amazed by this.”

Torture is one subject that animates Funke more than writing. A member of Amnesty International for 30 years, she calls herself a “political animal” and retains close links with two main charities: one for refugees in Bavaria, another for sick children in her native Hamburg. German culture, she says, lives in fear of “touching the oldness because it’s still sticky from fascism”.

And she insists that the darker subtexts in fantasy literature are often subconscious methods of coping with very real horrors. “There was a statistic once saying that people who read fantasy are more active in politics,” she says. “This might be because sometimes, if you read a lot about reality, you think you have done enough. I strongly believe in that. But I think it also refreshes a mind.

“We can’t stand to have reality all the time, I think nobody can. I remember reading my first Amnesty International report and how it broke the earth under my feet. A world like this, where children are tortured, you can’t deal with that every day.”

Funke is also a keen Green Party supporter, and aims to follow another Rowling lead by printing some editions of her books on recycled paper. “I try to be passionate about this,” she says, “but on the other hand I don’t want to be a writer with a message, because I think nobody listens to somebody with a message.”

Inevitably, Hollywood studios have taken a keen interest in her skyrocketing profile. Options have so far been taken on several of her novels, including Dragonrider and When Father Christmas Fell From Heaven, an old German publication which makes its English-language debut next year. But the first Funke adaptation in cinemas will be the screen version of The Thief Lord, which has just finished shooting in Venice.

“Cornelia is more appreciated in the English-speaking world, in America and England,” says the film’s director, Richard Claus. “The kind of appreciation you get as a creative person in America doesn’t exist in Germany, except for what is perceived as being high culture. Günter Grass? Yes, great. Cornelia Funke? Oh, that’s for kids.”

No wonder Funke is moving her family — husband Rolf, children Ben and Anna — to Los Angeles for three months next year so that she can take a hands-on role in developing a film version of Inkheart with New Line, makers of the Lord of the Rings trilogy. She has even begun courting Brendan Fraser for the role of Mo, the heroine’s father. Funke now has her own Los Angeles lawyer and has already blocked some superstar casting decisions. “In Hollywood,” her husband, Rolf Funke, says proudly, “they call her the woman with balls . . .”

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