Every high school student ought to read this book, and then turn off their portable devices and think about it for oh maybe as long as ten minutes and then attempt to verbalize what it's REALLY about. In the process, they might have some life altering insights into the society in which they live, not simply about life in the society which has evolved within the abandoned insane asylum on the Alphane Moon. This novel is classic PKD, full of his sly dystopian tropes. (All anyone needs to know about this author is that "You may be paranoid, but that doesn't mean They aren't out to get you.") Typically, PKD wrote in a hurry and he wrote for s/f pulp magazines, but Jonathan Swift couldn't be any more mordant and sharply observant of culture than this lately resurrected genius. The story does rush to the end and the characters begin to form and then fall flat--except for Lord Running Clam, the sentient slime mold--but what s/f buff really cares? PKD sets your mind spinning like a psychedelic top.
(And the 4 stars is only in relationship to other s/f, not in relationship to the whole universe of books. Don't much care for "Valis;" my personal favorites are "The 3 stigmata of Palmer Eldritch" & the glorious "Ubik.")