U.S. District Judge Deborah Batts temporarily blocked publication of the book, "60 Years Later: Coming Through the Rye," until she rules whether the book transforms Salinger's original creation enough that it qualifies to be published as a "fair use" of a copyrighted work.
A ruling was anticipated in the next 10 days. The book was scheduled for U.S. release on Sept. 15 but the court dispute was likely to delay that.
The hearing featured spirited arguments over whether Salinger's most famous literary character, Holden Caufield, is himself entitled to copyright protection and whether stopping publication of what some publicity materials referred to as a sequel would amount to a book ban.
Batts put Edward Henry Rosenthal, a lawyer for "60 Years Later" author Fredrik Colting, on the defensive in more than an hour of arguments over a lawsuit brought by 90-year-old Salinger, the Cornish, N.H., author who kept his reclusive reputation intact by not appearing in court.
She said she read both novels and agreed with Salinger that the new book was substantially similar to his own, published in 1951. Although there was little legal precedent to find that a character in a book with no drawings or photographs of him could be copyrighted, Batts said she believed Caufield could be.
"It's a portrait by words," she said. "It is difficult in fact to separate Holden Caulfield from the book."
She also disagreed with Rosenthal's argument that the new book provided obvious effective criticism of Salinger.
Batts said the issue was not that she was having trouble determining whether the criticism in the book was effective.
"Let me be clear," she said. "I am having difficulty seeing that it exists" at all.
"The Catcher In The Rye," which has sold more than 35 million copies, tells what happens to 16-year-old Caufield for several days immediately after he is kicked out of a prep school just before Christmas and decides to explore New York City before returning to his family home.
Colting, who lives near Gothenburg, Sweden, said in a court document that he did not "slavishly copy" Salinger when he wrote "60 Years Later," his first novel, under the pseudonym J.D. California.
"I am not a pirate," he wrote. He said he wrote the book as a critical exploration of the relationship between Salinger and his famous fictional character.
He said he used his book to transform "the precocious and authentic Holden into a 76-year-old man fraught with indecision and insecurity." The character, identified as "Mr. C," escapes from a retirement home and experiences similar to those Caulfield went through decades earlier.
He said his dedication of the book to Salinger was ironic.
"While I greatly admire Salinger as a writer, he is not the God-Author the public has created," Colting wrote. He also said it was a mistake that early copies of the book released in Great Britain included words promoting it as a sequel to Salinger's book.
During arguments Wednesday, Salinger lawyer Marcia Beth Paul called Colting's book "pure commercialism." She said 94 percent of the book was told in Caufield's voice and only 6 percent in Salinger's voice.
"This is a book about Holden Caulfield," Paul said. "It's a sequel, plain and simple."
She said it was wrong of the defendants to claim that blocking publication of the book because it infringes copyrights would be the same as banning a book. Salinger's book has frequently turned up on book ban lists.
"Make no mistake about it," Rosenthal charged in response. "This is banning the book."
He added: "To enjoin the book before a full exploration of the book is a prior restraint that raises very serious First Amendment questions."
Salinger has not published a book in decades and has rarely been heard from except when he takes legal actions to protect his works.
In a court document dated June 1, Phyllis Westbury, his literary agent, called Colting's book "wholesale piracy."
She said Salinger, who is now totally deaf, was recovering at a rehabilitation facility from surgery for a broken hip suffered in late May.
Westbury estimated that a sequel to Salinger's book would draw a $5 million advance and that his copyright was quite valuable but that "it is his wish not to further exploit it."
She included in her submission a rare comment he made in 1980 to The Boston Sunday Globe in which he said: "There's no more Holden Caufield. Read the book again. It's all there. Holden Caufield is only a frozen moment in time."
© 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
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