NEW YORK (Reuters) - An emotional J.K. Rowling said on Monday she had stopped working on a new novel because her creativity was stifled by a fan's bid to print an unofficial encyclopedic companion to her Harry Potter series.
The 42-year-old British author and Warner Bros. are suing independent U.S. publisher RDR Books, which plans to publish "The Harry Potter Lexicon," a 400-page reference book written by Steve Vander Ark and based on his popular fan Web site (www.hp-lexicon.org).
Rowling told a New York court on Monday that the demands of the case had caused her to halt work on a new novel. The author, who wrote seven novels about the boy wizard, said the stress has "decimated my creative work over the past month."
A lawyer for RDR books said the book by Vander Ark, a librarian who has spoken at Harry Potter conferences in several countries, would promote Rowling's series and not hurt sales.
Rowling, whose Harry Potter series has sold around 400 million copies, gave no further details about her new book, but has previously said she has half-finished a children's book.
When asked what Potter meant to her, the mother-of-three said: "I really don't want to cry, because I am British ... It's like asking how do you feel about your child."
"This is very personal to me," said Rowling, who wrote the first Potter book as a poverty-stricken single mother and is now estimated by The Sunday Times to be worth about $1 billion. "I am an author -- 17-years of my work is being exploited here. This is not about money."
Rowling has said she plans to write her own Harry Potter encyclopedia, which would include material that did not make it into the novels, and donate the proceeds to charity.
But she told U.S. District Court Judge Robert Patterson that she was now not sure if she had "the will or the heart" to publish her own encyclopedia and that if she did, "I would rather lock it away; it's associated with stress."
After she finished testifying, Rowling read a statement outside court. She said she felt strongly about the case because it "affects everyone and not just me."
"If books that plagiarize other works are permitted, authors, fans and readers stand to lose," Rowling said.
The lawsuit filed in October names Michigan-based RDR Books and unidentified persons. It seeks to stop publication and requests damages for copyright and federal trademark infringement and any profits to be gained.
Warner Bros. is a unit of Time Warner Inc, which owns the copyright and trademark rights to the Potter books.
"This is a case about the massive wholesale copying," Dale Cendali, a lawyer for Rowling and Warner said in court. "The lexicon is drawn almost entirely from Ms. Rowling's work."
Cendali said it was not a research guide as it lacked original material.
RDR publisher Roger Rappaport told the court that a timeline Vander Ark created was used by Warner Bros. in DVD releases of the Harry Potter films. He added that any reference to Harry Potter had been removed from the cover of the lexicon.
The company and Vander Ark have said the book would only promote the sale of Rowling's work and that Vander Ark's Web site, used by 25 million visitors, had been called "a great site" by Rowling herself.
"The lexicon is not a plausible substitute for any of the Harry Potter novels," said Anthony Falzone, a lawyer for RDR Books. "It's simply not plausible to argue that Ms. Rowling's sales will be hurt in any meaningful way."
He said Vander Ark's Harry Potter interest began "as a labor of love" and his expertise was so sought after that Warner Bros. flew him to the set of the fifth Harry Potter movie and used his lexicon everyday during production.
"It is, above all else, a reference guide," Falzone said. "Profit was never the point."
Writing by Michelle Nichols; Editing by Cynthia Osterman