Sequel to Updraft, which I enjoyed, but I have nearly put this down more than once. It’s plenty good, and the main character is a somewhat realistic 20-year-old (which is kind of annoying, but I guess good?). The problem is that I DO want to know how this world is constructed (at the moment, my best guess is that the towers these people live on and fly between are spines on the back of an enormous turtle), but I don’t care enough about the plot to keep reading to find out.
Update: I kept reading, I DID finish it, and I’ll tell you offline what I know about how the world is constructed if you ask nicely. Also, I don’t plan to read the third one. These books aren’t bad, but I just don’t care that much.