Books which should have Sequels

[Tigertots]

I'd like a sequel to Blubber, by Judy Blume: 20–30 years later, during the Halloween period, a glamorous, grown-up Linda tracks down Wendy, Caroline & Jill, and slaughters them! (It would be particularly apt, as the original story commences @ Halloween.) I did once suggest that on a website, but Judy herself said the sequel I had in mind would probably be too gruesome for most readers.

Are there any books which make you feel "I'd like to know what happens next in the characters' lives"?

I Capture The Castle. Would love to have read a follow-up!

The Changeover by Margaret Mahy. How does Laura grow into her powers? How does her romance with Sorry progress?

Joy in the Morning by Betty Smith who wrote A Tree Grows in Brooklyn. That too actually... The manuscript of Joy in the Morning was hugely cut for publication. I dream of a special edition with the missing quarter, but I doubt there would be the demand.