Philip K Dick - different people seem to respond to different aspects of his writing, the everyman heroes get good press generally. For me the appeal of Dick's writing was his obsession with two huge philosophical questions - what is human? and what is real?
This isn't a review of Philip K Dick's stories however. Andrew Niccol is a scriptwriter and director whose films also explore these questions, often very effectively. Four examples:
The Truman Show (2001, script AN, directed Peter Weir) The central character is unknowingly living on a huge sound set surrounded by actors, and is the central character in a life-long TV show. This scenario crops up several times in PKD's stories. Superb direction creates proper paranoia where traffic jams and mistuned radios become highly sinister; while Jim Carrey demonstrates comic timing without his trademark exaggeration and clowning, leading to a spot-on performance and a genuinely likeable character.
Gattaca (1997, written and directed by AN) this time the focus is on human identity in terms of genetics. This is hard sci-fi with only the tiniest extrapolations from the present to create a near-future society where your life is determined by quick and easy DNA testing. The central plot concerns the natural-born and genetically imperfect hero's attempt to join the space programme by borrowing DNA samples of a genetically perfect but injured athlete; however the subplots
explore the impact of DNA testing in everything from finding a partner to it's most familiar modern day use in CSI-style policing. Characterization is slightly cold in places; script is intelligent and clear, and visual imagery is often stylish and stunning (the two central characters live at the top and bottom of a house, connected by a helical spiral staircase).
S1m0ne - (2002, written and directed by AN) Pacino plays the director who fires his star actress and replaces her with a computer simulation. There are early hints that the simulation may itself be intelligent and have it's own agenda (boring) but in fact the film takes off in a much more imaginative direction - the director has to go to ever increasing lengths to convince the public (and fellow actors) of the reality of his vactress; meanwhile it becomes clear that Sim0ne is actually part of the director's personality.
Lord of War (2005, written and directed by AN) - the perpetrators of war crimes and other atrocities are often written off as inhuman monsters. I won't cite the obvious example as I am a firm adherent to Godwin's Law. In general this is a coward's way out of addressing the horrific truth that human beings are capable of this level of evil, or of thinking about why they might act the way they do. This film deserves full credit for taking this on - Cage's amoral international arms dealer character is given just enough emotional response to the consequences of his dealings that we can't see him as a robot, and are forced to struggle with the uncomfortable question of his motivation.