I Am Alive and You Are Dead: A Journey into the Mind of Philip K. Dick,
by Emmanuel Carrere.
I got this as an introduction to Carrere, but it revived an old interest in scifi. I hadn't realized how much scifi (Matrix, etc.) was influenced by Dick's fixation on the sense of self and its struggle to remain distinct from the environment.
I hadn't read Dick as an adolescent, it was all Harry Harrison, Asimov, and Dune. But it turns out Dick had debilitating paranoid delusions. Carrere makes a strong case that Dick really believed he was receiving messages from God about how to launch a new age, although he could also use that delusion as a literary source by critiquing it from the skeptical side of his brain that remained.
The style is fictionalized biography. Carrere researched deeply to establish a scene, but then invented a lot of inner thoughts that he believed must have been going on. The effect is very convincing. I trusted that he was creating a reasonable facsimile, consistent with verifiable evidence.
One chapter I glossed through because it became too lit crit -- taking the ideas way too seriously. Dick is compelling as an extraordinary, autodidact pulp writer, not as a philosopher. But I really enjoyed the rest of the book, especially how a tortured psyche was integral to the stories that swirled out. You may be interested to know he only dropped acid once. Didn't need it. There's also plenty of titillating debauchery and his painfully pathetic personal life.
Now that I read the bio, I'm less bored with Amazon's Man in the High Castle