I have always felt that PKD was the type of author who could really blow me away with his mind-expanding ideas. Unfortunately his other novels that I previously read struck me as overrated, as the ideas failed to gel into coherent stories. However, he hits the bullseye with "A Scanner Darkly" which has to be one of best novels. Taking place in a dysfunctional near-future, the story revolves around the new drug called Substance D. (The only glitch in this book is that PKD places the story in the 1990's, and PKD's vision of the future from back in the 70's is a bit distracting in its inaccuracies). Substance D causes a disconnect between the left and right sides of the brain, causing a split personality syndrome in which both of the user's selves are active simultaneously and compete with each other. The main character, Bob Arctor, is an undercover cop who poses as a dealer, and his undercover self has been assigned to watch his dealer self. At first he realizes the bureaucratic mistake, but as he falls deeper and deeper into the world of Substance D, Bob can no longer perceive the difference between his two selves and descends into a schizophrenic nightmare. Bob's deteriorating state becomes a very disturbing tract from PKD on the nature of one's identity, the destruction of the self through drug abuse, and the reality or un-reality of the self's replacement. Also, in PKD's future the drug war becomes a class war, as the "straights" need the users as a class of non-persons to manipulate and to experiment on. This may just be the way users see the world, and PKD shows us that it may not be a farfetched conspiracy theory. This is a truly troubling look into the world of damaged and ruined minds, from a man who just may have been there himself.