After reading Ubik, I wanted to read another PKD novel, and I happened to have a copy of VALIS that I'd bought more than a decade ago.

First, let me say wow.

From what I can gather, VALIS has many autobiographical elements, and if so, PKD was a deeply messed-up dude. Dick himself is the schizophrenic, drugged-out narrator, and the first half of the novel leaves the reader wondering which end is up. Things come together and the rules of the novel's universe become more clear in the second half, but it's still a total brain trip.