By Christine Kearney

NEW YORK (Reuters) - A book billed as an unofficial encyclopedic companion to the "Harry Potter" series infringes copyright and attempts to cash in on the successful brand, author J.K. Rowling and Warner Bros. said when they filed a lawsuit on Wednesday.

The 400-page book -- "The Harry Potter Lexicon" due to be released by RDR Books on November 28 in the United States -- had inappropriately referenced Rowling's fictional characters and universe, Rowling and Warner Bros. said.

RDR Books said the author of the reference book, Steve Vander Ark, based it on his fan Web site, www.hp-lexicon.org, that was used by 25 million visitors and had been called "a great site" by Rowling herself.

In a statement on Wednesday, Rowling said even though she loved fan sites, she hoped to write "the definitive Harry Potter encyclopedia, which will include all the material that never made it into the novels" and donate the proceeds to charity.

"I cannot, therefore, approve of 'companion books' or 'encyclopedias' that seek to pre-empt my definitive Potter reference book for their authors' own personal gain," she said. "The losers in such a situation would be the charities that I hope, eventually, to benefit."

The lawsuit names RDR Books, an independent publisher based in Michigan, and unidentified persons as defendants. It seeks damages for copyright and federal trademark infringement and any profits to be gained from the book.

"The infringing book is particularly troubling as it is in direct contravention to Ms. Rowling's repeatedly stated intention to publish her own companion books to the series," said the lawsuit, filed in federal court in Manhattan.

Roger Rapoport, the publisher and owner of RDR Books, said Vander Ark, a librarian, had spoken at Harry Potter academic conferences in Britain, Canada and the United States and that a timeline he created was used by Warner Bros. in DVD releases of the Harry Potter films.

The forthcoming book "only promotes the sale of J.K. Rowling's work and we intend to publish on schedule as planned," said Rapoport.

Warner Bros., a unit of Time Warner Inc. that owns the copyright and trademark rights to the seven "Harry Potter" books, said in a statement it was seeking to protect Rowling's right to produce a future companion book.
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