Ubik by Philip K. Dick
Among the greatest writers of sci-fi, few were more supremely talented and gifted with genius than Philip K. Dick. Ubik is one of his handful of masterpieces, one of few science fiction novels to make it to TIME Magazine’s 100 Best Books since 1923. The story takes a science fiction framework to discuss the nature of God, in this case coming in the form of a sort of aerosol spray that fixes everything. It has parts that make it feel like a horror story, but it really is a perfect example of existential science fiction that has more room for discussion than can be believed for a relatively low word count.