NEW YORK -- Harry Potter author J.K. Rowling is trying to stop a fan of the books from publishing an unauthorized reference work, called the "Harry Potter Lexicon."

It's being put together by Steven Vander Ark, the editor of a Web site containing essays and other material created by fans. It includes a list of spells and potions found in the Potter books, along with a catalog of magical creatures and a who's-who in the wizarding world.

Rowling's seven-book saga has yielded blockbuster sales worldwide and spawned a hit film series starring Daniel Radcliffe as the boy wizard.

In the past, Rowling has singled out the Web site and its creator for praise.

But now, she's filing a lawsuit in New York, saying she feels betrayed by her fan.

"I am deeply troubled by the portrayal of my efforts to protect and preserve the copyrights I have been granted in the Harry Potter books," she said in court papers.

And she said that she's especially troubled by the claim that because Rowling has accepted free, fan-based Web sites in the past, this effort should be allowed.

Rowling said that if the Lexicon is published, other authors will have to protect their work more vigorously against Internet material that's based on that work.

Rowling also said that she's planning to publish her own, definitive Harry Potter encyclopedia.

Rowling released the final Harry Potter book, "Harry Potter and the Deathly Hallows," last July.

The sixth Harry Potter film, "Harry Potter and the Half-Blood Prince," is due in theaters in November.