The first of three novels in what is described in many publishers' blurbs as a "
trilogy" of "Valis" novels. In addition to the two novels published sequentially following
VALIS,
The Divine Invasion and
The Transmigration of Timothy Archer, at least one other novel in this vein survived and was published,
Radio Free Albemuth.
It's been quite some time since I last read all four novels, so please consider much of this tentative until I've refreshed my memory, and have made revisions.
In all of these novels, Dick intertwines themes that were prominent in the main body of his work, in particular, dealing with the distortion and intentional manipulation of reality (and of human memory, sometimes individually, sometimes on a wholesale basis) by hidden forces, and other elements often identified with clinically-defined paranoia with much more explicit elements of autobiographical detail.
One might in fact argue that the four novels are closer to versions of the same novel than they are to what one expects typically of a trilogy. In the "Valis" novels, taken as a group, a much more Christian note is sounded. Be warned, however, that it is often a reconstruction of a particular and often quite peculiar ideolect of gnostic Christianity, not any form of Christianity as known to most who embrace that label and apply it to themselves today.
On the one hand, Dick is dealing here with a very personal, and quirky set of icons and symbols that arise from wholly personal events that he tells us have happened to him (or to various thinly veiled versions of himself) through his life. And if you then go back to read Dick's novels before Valis you will find much of the same typology developing through nearly all of that work as well.
On the other hand, he is telling, in incredibly compressed form, much of the intellectual and religious history of the Western world since at least the Decline and Fall of the Roman Empire.
Autobiography, dead girlfriends he can't seem to let go of, and the history of Christian-influenced culture, all rolled into one seamless fabric. That's Philip K. Dick for you.