Is it a fantasy novel, a science fiction novel, or a crime novel? Sure. Why not?

It's nigh impossible to discuss this modern classic in any detail without spoiling some vital piece of the narrative. The premise is simple to explain, although fairly difficult to imagine: what if two cities, for reasons lost to history, both reside in the same geographic area, sharing some streets and even some parks and buildings, but being legally and technically different countries? And, what if they had taken that to the extreme of making it illegal to even recognize the buildings, people, and infrastructure, the sounds and even the smells, of the "foreign" city? People may live physically next door to each other, yet for cultural reasons be forced to "unsee" each other as they pass in the street.

And then someone gets murdered, and it's unclear who has jurisdiction, or if anyone does.

Yeah, it's trippy as all get out, but worth the mental energy.