Again, Christopher races through. I take it now that his objective is to have the kids go all the way around the world by the end of the trilogy. The characters are interesting, but the pace is too rapid to really enjoy the journey. No sooner do they reach any place than they're on their way to another, and we never really settle in. Christopher's alternate civilizations are fairly thinly sketched in, and generally resemble their historical analogues, with very little technological or cultural development. Native Americans are as they were. The Inca, Aztecs, and Maya have merged, but not developed. The two boys follow each other, but for no clear reason.
I've always been a fan of Christopher's young adults, but this is one of his least successful efforts. Smooth, but not satisfying.