JD Salinger has not published a book in decades
A US judge has questioned whether a new book, promoted as a sequel to JD Salinger's The Catcher In The Rye, would harm Salinger's copyright.
Lawyers for Swedish novelist Fredrik Colting, who wrote 60 Years Later: Coming Through The Rye, are appealing against a US publication ban.
Judge Guido Calabresi called the spin-off a "rather dismal piece of work".
He added: "Anybody can just go on the internet and get the London edition." The book came out in the UK in June.
A panel of three US appeals court judges, in New York, are considering whether the new book could cause irreparable harm to Salinger, which would be legal grounds for blocking US publication.
In July, Judge Deborah Batts issued a preliminary injunction, indefinitely banning the publication, advertising or distribution of the book in the US.
Judge Batts concluded that Mr Colting's novel too closely mirrored Mr Salinger's 1951 classic.
In her 37-page ruling, issued in Manhattan, she said the main character in Mr Colting's novel - Mr C - was "an infringement" on Mr Salinger's main character, Holden Caulfield.
Mr Colting claims his book, featuring a character based on Salinger's hero, is a literary commentary not a sequel.
"Our position is this is not a sequel," lawyer Edward Rosenthal told the appeals court. "This is a highly transformative work about the relationship between Salinger and his character."
He added that there was no evidence his client's book would limit the value of any possible Salinger sequel.
Speaking in court on Thursday, Mr Salinger's lawyer, Marcia Paul, reiterated that her client "does not want to authorise a sequel or a derivative".
She added that over the years the author had turned down requests to adapt the original book for the screen by film-maker Steven Spielberg and producer Harvey Weinstein.
The Catcher In The Rye, first published in 1951, is a tale of adolescent alienation and has become one of the most influential American novels of the modern era.
The novel sees Caulfield wandering around New York and railing against the establishment, following his expulsion from boarding school.
Mr Colting's novel sees 76-year-old Mr C - who the author has admitted is based on Caulfield - escape from a retirement home and head to New York.
Both books end near a carousel in Central Park.