Although a difficult read sometimes, it was dark and paranoid and was engaging throughout.
I would recommend this to any (potential) Philip K. Dick fan.
I came across the book after someone recommended that I see the film. This was actually the first time I've read the book after seeing the film, but I was very impressed with both.
Mind- and reality-bending drugs feature again and again in Philip K. Dick's hugely influential SF stories. A Scanner Darkly is the novel that cuts closest to the bone, drawing on Dick's own experience with illicit chemicals and on his many friends who died through drug misuse. Nevertheless it's blackly farcical, full of comic- surreal conversations between people whose synapses are partly fried, sudden flights of paranoid logic, and bad trips like the one whose victim spends a subjective eternity having all his sins read to him, in shifts, by compound-eyed aliens. (It takes 11,000 years of this to reach the time when as a boy he discovered masturbation.) The antihero Bob Arctor is forced by his double life into warring double personalities: as futuristic narcotics agent "Fred", face blurred by a high-tech scrambler, he must spy on and entrap suspected drug dealer Bob Arctor. His disintegration under the influence of the insidious Substance D is genuine tragicomedy. For Arctor there's no way off the addict's downward escalator, but what awaits at the bottom is a kind of redemption--there are more wheels within wheels than we suspected, and his life is not entirely wasted. In a just world this harrowing novel, the 20th selection in the Millennium SF Masterworks, would have matched the sales of Trainspotting. --David Langford