poliphilo

Two city states with very different cultures occupy the same space. Citizens of one state are conditioned to "unsee" everything that appertains to the other- which gets to be really tricky in "crosshatched" areas where the two rub up against one another and the roads carry traffic of both nationalities.

This excellent dystopia is animated by a fairly conventional police thriller which ends with one of those stand-offs where- instead of getting on with it and trading shots- the detective and the villain jaw for pages about how and why the crime was committed.

World-building: A++

Characterization and plotting and all that novelistic stuff: B-