I would recommend, and you are welcome to ignore should you choose:
Ubik
Flow my tears, the policeman said
Dr Bloodmoney
Radio Free Albemuth
Time out of joint
A scanner darkly
Mary and the giant
And finally as an aside, 334 by Thomas Disch.
Fun fact: Dick shopped Disch to the feds for in his view pedalling anti-American views. These letters are fascinating - and Radio Free Albemuth might ring some bells.
http://www.lettersofnote.com/2010/07/neo-nazis-syphilis-and-...
PKD has an uncanny grasp on the reality-busting nature of our current reality, and the above books are a decent primer in his way of thinking. The list is by no means complete, just what trips out of my head as “Good PKD”.
His non-sf works, like Mary and the Giant and Confessions of a Crap Artist, I did not understand in the slightest as a younger man. Now I read them, and their realities are palpable, sordid, tawdry, and utterly real.
Most likely the latter, but honestly, I don’t know. Disch’s work did change fairly radically and suddenly, but that’s not to say there was an external influence.