I read a children's novel many years ago about a boy who lived in some sort of fantastical world. There are a few things that stick out in my memory:
- The major conflict lay between the "boys" and the "girls" of the world, each existing as their own faction. The only inhabitants of this fantasy world were children, no adults.
- During the night, all the children would "nap" on various blankets and such
- I think vehicles (cars, motorcycles, or maybe bicycles) may have been sentient in some way, if not sentient, they were valued by the kids a lot in their "battles" between factions
- The end of the book concluded with the protagonist boy getting on a train. Everyone agreed that this train meant you'd leave and never return, and then after the boy got on this train toward the end of the last chapter you realize that he's sitting on a train in "our" world and is about to stop being a child and begin to explore being a "grown-up."