One of my favorite books. The first time I read itThe ambiguity is one of my favorite aspects of the book.I thought that is was "magic," one city breaching into the other; when I read it again a year later, I was convinced it was just two cities in the same geographic space whose citizens learned to ignore each other, or fight each other for space. I don't think there is a "right" way to interpret the cities. Though, the mythology and third city do seem to suggest that "magic" is the appropriate interpretation.
When you finish let me know what you think. BTW that cover is fucking awesome.
There definitely is a right way to interpret the book.
They're just one city that the inhabitants have psychologically trained themselves to perceive as partitioned.