Books that need a sequel

My first thought on reading this prompt for Long and Short Reviews was “They don’t.” I have often read or watched sequels and wished they didn’t exist – “Glass” leaps to mind. However, I did manage to think of a couple of possibilities.
A Return to Sanditon (Anne Toledo). This was a completion of the original Austen fragment and manages to develop and introduce so many characters that I would happily follow them into a sequel.
Airframe/Prey (Michael Crichton). Both of these novels created worlds which interested me and had potential for more, especially Prey which was deliberately left open-ended. Airframe was tied off more neatly but I enjoyed the aviation so much I would willingly read more.
Requiem (Lauren Oliver). This was a sequel in itself, but one which left a lot of loose ends which I would have liked tying off. The world of deliria and the characters’ relationships still had a lot of work to be done.
And I would always like more Sherlock Holmes sequels, as long as they’re done well.
So what would you like to see?