Famed British writer J. K. Rowling, who is trying to stop the publication of an unauthorized Harry Potter lexicon because of copyright infringement she calls “wholesale theft,” told a Manhattan court Monday that being betrayed by a fan – the author of the encyclopedia – has caused her “heartache.”

J. K. Rowling testified before a New York courtroom on Monday in a lawsuit to block publication of “The Harry Potter Lexicon,” a 400-page book authored by Steven Vander Ark, editor of fan website www.hp-lexicon.org, that was to be published last November via Michigan-based RDR Books.

The creator of bespectacled wizard boy Harry Potter appeared emotional during her 3-hour testimony and even fought back tears, reports the New York Times. She told Judge Robert P. Patterson, who is hearing the case without a jury, that the book amounts to “wholesale theft” and is a rip-off of nearly 20 years of her hard work.

Rowling said she has read the manuscript and that she considers it a blatant plagiarism of her own writing. The 42-year-old mother of three said this was not a matter of money but rather of 17 years of her life being pilfered.

The first Harry Potter book she wrote marked a change of luck for Rowling; she was a single parent living on state benefits who soon became one of Britain’s favorite billionaires.

“I am an author - 17-years of my work is being exploited here. This is not about money,” the writer told the court.

Rowling went on to describe the turmoil, the “stress and heartache” she has been feeling since learning of Ark’s plans to publish the unauthorized lexicon. “It has really decimated the demands of my creative work for the last month,” she testified, as quoted by the Times.

“You lose the threads, you worry if you’ll ever be able to pick them up again,” she said.

As to Ark’s book, which is based on the website, Rowling said it was “sloppy, lazy,” and full of errors. She said the only reason it was being published in the first place was to bring the publisher and Ark “a fast buck.” The intended price for the book was $24.95.

The Times adds that the book’s publisher, Roger Rapoport, testified that he had heard of Ark and his passion for the Harry Potter universe from his local newspaper and that he approached the passionate reader, who is also a trained librarian, to pen a book. Rapoport said he had agreed to cover the costs of any potential lawsuit.