My fascination with PKD is his fascination with the nature of reality which I share. "How to Build a Universe..." is a long read but packs in a lot of ideas in essay format. I feel like most of his core beliefs are contained in it. My favorite quality of PKD is that he does not present any idea as something true or something he wants us to believe in. He merely reports what he experiences and then asks himself and us if this could be real and if so how?
Between PKD's "If you find this world bad, you should see some of the others" talk (https://youtu.be/Q7SxTm_LQW4) predicted the plot of The Matrix back in 1977, and his letters in "Exegesis," his secret to world building was based on remembering it from visions.
Welt Am Draht "predicted" The Matrix in 1973, and it was based on Simulacron-3 which also "predicted" The Matrix, written in 1964.
The Matrix was not a specifically unique concept, it was just unfamiliar to audiences at the time. That isn't to say that there isn't something especially good and powerful in it's blend of the aesthetics and themes that Welt Am Draht and the remake The Thirteenth Floor didn't have.
