I don’t know if Cory Doctorow has read the “fantastic 1981 novel”, but I have (decades ago) and as I recall the plot of the book and the plot of the movie are very different from each other. The author of the book didn’t write the screenplay and I doubt he had much (if anything) to do the character designs in the movie. So even if he has the rights to his novel back, it’s not at all clear to me that he could just make (or sell a license to make) a straight, recognizable sequel to Disney’s movie without getting back into bed with Disney, and clearly Disney isn’t interested or they’d have done something by now.

Sometimes (often) the original is the best. Sequels are just milking more money from the concept and rarely match the original let alone exceed it. It's the laziest sort of movie-making.

I read the "fantastic 1981 novel", too, and you know what? It wasn't very good. It had a lot of really interesting world-building and some cool ideas, but the characters were flat and the central mystery was terrible. Despite common wisdom, the book is not always better than the movie.

I mean, given that Disney wasn't doing anything new with Roger Rabbit, I'm glad he got the rights back. But I think part of the reason that very little new material got produced is that the first movie was kind of lightning in a bottle. It's possible other production companies would have had to be involved to get something new done, depending on how the rights were parceled out. (We're all talking about Disney here because that's who Doctorow focused on, but it was a co-production with Spielberg's Amblin Entertainment.) And I think you're right that he's unlikely to have the rights to do a sequel that's too close to the original.

Disney definitely owns the character designs, so Roger and Jessica Rabbit will have to look different if a new movie is made using the IP owned by the book's author.

>clearly Disney isn’t interested

often big media companies aren't interested in exploiting specific properties if there is ongoing litigation regarding them.

Yeah the Roger Rabbit is a miracle where multiple major studios came together and allowed their IP to be in the same work. Disney, Warner Bros, Fleischer Studios, Harvey Comics, King Features Syndicate, Felix the Cat Productions, Turner Entertainment, and Universal Pictures/Walter Lantz Productions all agreed to share their characters. One of Steven Spielbergs great accomplishments was negotiating this. With how protective these studios are about their IP anymore I doubt we'd see anything close to the Roger Rabbit movie sadly.

Not to mention some of the actors have passed like Paul Reuben who really sold the cartoon aspect of Roger Rabbit.