I have vague memories of reading a story/book as a child, ~15 years ago.
The vast majority of the world's inhabitants are ghosts
These ghosts turn normal humans into other ghosts by simply touching them
I think maybe they only come out at night?
- Ghosts are allergic to wood. Simply being touched is enough to 'pop' them (permanent disappearance)
- There's a super-hero type dude that has a 'wand' (stick) and protects everyone from the ghosts
- I think the population hide in old wooded warehouses at night
- There's a big mansion made entirely of glass
- There is only one tree left in the world, the rest having been cut and burned to make the big glass mansion. It is guarded 24/7 by the ghosts
- I think they eventually get a bird to nick some seeds, grow more trees and kill all the ghosts