JOANNE Rowling, the Edinburgh author who wrote her first novel in a city cafe, has taken a children's book to the top of the British hardback best -sellers' list.

The former part-time teacher at Leith Academy had her latest book published only last week.

The book, Harry Potter and the Chamber of Secrets, is the second featuring the eponymous hero and has knocked Terry Pratchett's Last Continent into second place.

Yesterday, Rowling, 32, expressed her delight at the success, but insisted that the praise of her sister, Di, was more important.

"She was the first person to read the books," Rowling said.

"She's much better read than I am, so it meant a lot to me that she liked it."

Rowling, who was brought up in Gwent, moved to Edinburgh to be near her sister when her marriage to a Portuguese television producer broke down in 1993, shortly after her daughter Jessica was born.

She lived in a dingy flat and sought refuge at Nicolson's cafe in the city centre, where she wrote while Jessica slept.

Rowling described writing Harry Potter and the Philosopher's Stone as a means of escaping poverty and staying sane.

Her fame has now made it awkward for her to work on her books at Nicolson's, but she has continued to write in cafes around the city and said: "I feel a bit superstitious because that's how I wrote the first book and I don't want to break the run of luck.

"I've been amazed at how adults came up to me on the publicity tour and asked for autographs for themselves."

Rowling feels her flawed hero, Harry, appeals to people of all ages. "He has weaknesses but he's not a turn-the-other-cheek sort of lad. There's a lot of me in him."

Rowling went back to visit some of her former English pupils at Leith Academy after the success of her first book.

She said: "They avoided the issue for half of the class and then someone said, 'Miss! You're rich now, eh?'"

The author, who now lives in the centre of Edinburgh, said: "I told them that I wasn't rich but I'm a lot richer."

However, Rowling feels that reports of her life as a single mother have been exaggerated - she drew benefit only for six months until she was driven to find work .

She conceded: "I'm slightly offended that people are surprised that a single mother could do this. There are thousands of single mothers out there who all do two people's jobs at once and often a third paid one as well."

She is now negotiating a deal for a film of her first book, but said that she is in no hurry to sign away her character: "If it happens, then it will be because I know that they will be really true to the books."

Rowling expects to complete her next book, Harry and the Prisoner of Azkaban, this week, while writing for a web site produced by her publisher, Bloomsbury, in response to more than 1,000 letters from fans .

She said: "The site will let people see material that hasn't made it into the books and see how the other books are developing, but I won't give too much away."

The GBP 100,000 advance for the American edition of her first book put her ahead of another best-seller, John Grisham, whose first novel, The Firm, cost publishers GBP 70,000.

But she has no plans to branch into more "serious" literature and said: "People say: 'When will you write an adult book?' as if that's the pinnacle of achievement. But if I remain a children's writer for the rest of my life, that's OK by me."

Copyright 1998 The Scotsman Publications Ltd.