The working title for The Divine Invasion was VALIS Regained. I would have liked that. As a sequel to VALIS, it's somewhat unsatisfying; it shares no characters, no plot lines. But the strange central idea of Dick's fictional-universe-cum-actual-philosophy is here: that God was exiled to outer space millennia ago, and that we've been living in an imaginary universe ever since. The Divine Invasion stages God's return to Earth--something attempted, but not achieved, in VALIS--as a young boy, Emmanuel.
Emmanuel, like Christ, is the product of a virgin birth, this time on a remote planet where people live in pods isolated from one another and separated by an inhospitable wasteland. The protagonist Herb Asher helps Emmanuel and his mother, Rybys, return to Earth, but malicious government forces attack the incoming ship, forcing the injured Herb into suspended animation. The crash also inflicts brain damage and amnesia on Emmanuel, who must slowly remember that he is God and recover the true extent of his power. Like all of Dick's books, there are strange tangents that intersect with the main plot at oblique angles, including a popular diva who sings 16th century English folk ballads. Also, the prophet Elijah's there, and he's like three thousand years old.
The Divine Invasion is not as satisfyingly bonkers as VALIS, mostly because it lacks the layered biographical irony of that book. But I did really love the ending, which dramatizes the choice Herb has to make between the God-child Emmanuel and a seductive goat-creature identified with Belial, or Satan:
Gray truth, the goat-creature continued, is better than what you have imagined. You wanted to wake up. Now you are awake; I show you things as they are, pitilessly; but that is how it should be. How do you suppose I defeated Yahwah in times past? By revealing his creation for what it is, a wretched thing to be despised. This is his defeat, what you see -- see through my mind and eyes, my vision of the world: my correct vision.
Did I mention the goat communicates by telepathy? It's weird. But it also provides an insight into what Dick was trying to do by writing science fiction, and why he so frequently layers his work with false, imagined worlds (like the post-WWII world of The Man in the High Castle, for example). Belial presents a choice between the "gray truth" and the hopeful ideal world that Emmanuel, damaged and immature, offers instead. At the end of the book--spoilers here--the goat-creature is killed when someone loves and pities it. To pity the world of "gray truth" is to imagine a better one, and to kill it by imagining. I like that.