Reed has done several Great Ship novels and stories. A huge (maybe Jupiter sized?) primordial spaceship that orbits the galaxy comes under the control of humans. There are numerous environments within The Great Ship, in this case a sealed sphere. I am not sure I ever got an accurate picture of how this environment's trees, reefs, and sun were laid out - a diagram would have been nice.
I realized that most of these Great Ship stories are artificial worlds stories. Somehow about 1/2 way through these stories I was strongly reminded of Philip Jose Farmer's World of Tiers stories, although there aren't that many similarities.
The book moves along pretty well. 4 alien children with possibly revolutionary powers completely destabilize society, as factions vie to control the children to exploit their powers. The main child that is follows is sometimes sympathetic, sometimes not.
The ending to the story happens quickly and completely out of left field. It seems to be suggesting more novels with these characters, but in a completely different environment. Again, I was really kind of thrown by the ending. But, Reed writes well, it was a diverting story, not sure there's much edge there. Reed I first remember for some totally edgy stories in Year's Best. So, still worth a read.