Dan Brown, best-selling author of The Da Vinci Code, has won a court ruling in New York against writer Lewis Perdue over charges of plagiarism.
Dan Brown's The Da Vinci Code has become a global phenomenon
Mr Perdue claimed The Da Vinci Code plagiarised elements of two of his novels, Daughter of God, published in 2000 and 1983's The Da Vinci Legacy.
He sought to block future distribution of the book and forthcoming film, as well as $150m (£84m) in damages.
But the judge said any similarity was based on "unprotectable ideas".
"A reasonable average lay observer would not conclude that The Da Vinci Code is substantially similar to Daughter of God," wrote Judge George Daniels, who made a detailed analysis of all three works in question.
"Any slightly similar elements are on the level of generalised or otherwise unprotectable ideas," said Judge Daniels, of the US District Court in New York.
Mr Perdue said he would appeal against the ruling.
"I have no doubt that we're going to see this overturned on appeal because there have been copyright infringement cases where the parties had less to go on than we have and they were able to have their cases overturned," he said.
Mr Perdue launched a web site documenting Mr Brown's alleged plagiarism, after receiving emails from readers pointing out the similarities between their works.
"I felt violated, like somebody had broken into my head," he said. "It took away the results of my creativity."
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He alleged that Mr Brown copied the basic premise of Daughter of God, including notions of a "divine feminine" and the transition from a female to a male-dominated church under Roman Emperor Constantine.
Mr Brown, whose controversial best-seller has been the subject of furious religious debate, subsequently sought a legal ruling stating that his book did not infringe Mr Perdue's copyright. Mr Perdue countersued.
The Da Vinci Code has sold more than 17 million copies and been translated into 42 languages.
A film based on the novel, starring Tom Hanks and Audrey Tautou, is due out in 2006.