Like Palmer Eldrich, PKD here is questioning the nature of his characters' reality and using it to spin a sort of nightmare in slow-motion, taking the pervasive colonization and control of that earlier book and adding a sort of decay or elemental regression. The plot itself, like Eldrich, is sort of superfluous except to keep the action going and create room for the mood to do its work. A quick, unsettling read that I don't want to spoil too much of for anyone else.