"One of the most theologically probing of all of Dick's books" it says in the blurb. That may well be true.
I'm not so firm, theologically, but there sure are a lot of refences in the book, be it in the form of direct quotes or the "appearance" of people connected to the theme.
If you, as a reader, wanted to be on par with the author on this book, you would need to research 13 people and their life and works, including jazz musician Herbie Mann or the writings of St. Paul.
Some, like Malcom X or James Pike are obvious (wiki some of the names, if you like), but the similarity of the character "Harold Agee" to the real "James Agee", one of the most influential film critics in the America of the 1940ies, who was a close friend to the Episcopal priest Father "James Harold Flye" are less so.
They might even be coincidences.
Given Dick's attention to detail, I doubt it. And then there is "Herb Caen", who could be the influential columnist of the same name and one "Michael Harrinton", who may well be the real "Edward Michael Harrington", a socialist, writer and political activist, born in the same year as Dick and who attended the same university even ...
Yes, it was fun doing this little bit of research. It's enlightening. In some shape or form.