Someone (not J.D. Salinger) has written a sequel, or perhaps a re-evaluation, of J.D. Salinger's famous novel The Catcher in the Rye. J.D. Salinger is suing to suppress the new book.
Possibly the new book will manage to find a safe harbor from actions for copyright infringement by claiming to be a "parody." Possibly not.
But, just as in the case of The Wind Done Gone, so in this case the question should not have arisen at all. If Congress had kept faith with the reading public, and kept the duration of copyright in pre-1978 works at 56 years, the term that applied when The Catcher in the Rye was first published, the novel would now be in the public domain. Authors of sequels and other derivations would not need to be trying to navigate the complexities of fair use. Salinger's novel would instead be "free as the air to common use."