I love it when authors do that - keep writing about the same "universe," in science fiction terms. When I realized Stephen King characters interacted with each other from novel to novel, I was delighted. It felt like a guilty pleasure, like he was breaking some rule. I guess because I've heard it said that "readers just want you to keep writing the same book over and over" and I got the impression authors were supposed to want to start from scratch each time. (Though usually certain characters reappear, even if they're not "supposed" to be the same person.) I love the idea of books about the relatives of characters from a book I've already read.

Me, I knew as I was writing "A Singular Being" that I'd like to write about that universe again, though I was thinking of the species/planet, not necessarily the same character. But now I'm thinking about a novel that will be in part a romance between Pneumia, the young scientist protagionist of "Being" and the guy who delivers the fresh have-to-think-of-alien-sounding-name-for-clams-mussels-oysters-shrimp that my intelligent and pychic sea creatures eat.