The Coraline author was planning to mark the occasion by scripting a special story for the comic book series, but failed to negotiate with DC Comics, SciFiWire reports.
"I wanted to do a 20th anniversary story, and it broke mostly because DC Comics would have loved me to do a 20th anniversary story at the same terms that were agreed upon in 1987, when I was a 26-year-old unknown," he said in an interview with Jam! Showbiz.
He added: "And my thought was, 'You know what, guys, it really doesn't work like that'. I wasn't going to do a deal at the same terms we had in 1987, and they were not willing to do any better than that."
It was recently announced that director Neil Jordan will be adapting Gaiman’s novel The Graveyard Book into a film.