Celebrated author JK Rowling asked a US court Monday to block publication of an encyclopedia based on her blockbuster 'Harry Potter' series of children's books, calling it "wholesale theft".

"This book constitutes a wholesale theft of 17 years of hard work," Rowling testified in a Manhattan District Court on the first day of a trial that was expected to last most of the week.

"It was all my life, apart from my children," she said close to tears, adding that she felt "extremely shocked" upon learning about the derivative 'Harry Potter Lexicon' by Steve Vander Ark.

She accused publisher of the 'Lexicon', RDR Books, Michigan, of altering her literary characters' integrity and their fictional universe, saying that had prompted her lawsuit, rather than monetary compensation.

Vander Ark is a Rowling admirer who runs a website dedicated to the 'Harry Potter' collection of books he has read many times over, according to his lawyer.

Rowling said she supported Vander Ark's website in the past, but that on learning of his upcoming book, which has a planned sale price of $24.95: "I did feel a degree of betrayal."

Rowling and Warner Brothers, the Hollywood film studio that has translated her hit book series to the big screen, accused the lexicon's publisher of undermining the integrity of her work.

But Anthony Falzone, the attorney representing RDR Books, countered that the encyclopedia, meant to be a companion to the books or the films, not only does not diminish the original novels, but actually enhances the enjoyment of them.

"If this book is suppressed, the public will lose a useful reference guide," Falzone said.

"The question here is to decide whether Mrs. Rowling has the power to make the 'Lexicon' disappear," he said, asserting that the book "is not a plausible substitute to any of the 'Harry Potter' novels."

Rowling, however, said that she had planned her own reference guide cataloguing the characters and events in her highly popular book series, which has sold almost 350 million copies around the world in some 65 languages.

Dressed in dark, pinstriped suit, Rowling admitted she was nervous on her first ever appearance in court.

"Writing a novel is a labour of love," she said. "Writing an encyclopedia is something different."

She said she expected that her own 'Harry Potter' encyclopedia, done "properly" would take her about "two to three years", adding that the proceeds would go to children's charities.

She slammed the 'Lexicon' as an artless rip-off.

"The Lexicon is not a quality book," she said. "There are places in which Mr. Vander Ark has quite plainly not understood the ('Harry Potter') book," she said.

AFP