"Transmigration" is the final book published by PKD. He passed on in March of 1982 after a series of strokes. The book was published the year before and while not originally to be included in the "Valis" trilogy, its subject matter of religion/philosophy and belief fits very nicely with the trilogy. The third book titled "The Owl and Daylight" was never finished.
In this book PKD seems to address the public speculation of his not being able to create a woman character that is more than 2 dimensions. I read one critic's review in which was asked, "Can't [PKD] have a woman character without talking about her breasts?" So I'm guessing that since this book was written from the point of view of Angel Archer (female) that he can create a multi-dimensional female character. In this spiritual journey Angel Archer (I like the play with words there Archangel) must decide what is real what to believe and how it all works in with life. And no her breasts are not mentioned once.
Angel is heading to a spiritual retreat the day John Lennon was shot and this starts her soul searching through the loved ones she lost and why they died many years before. Her Husband, Jeff Archer commits suicide after a trip to find the true Jesus as told in some lost scrolls found near where the Dead Sea Scrolls were found. Jeff was on this trip with his father, Episcopalian Bishop Timothy Archer, and the bishop's mistress, Kirsten Lundborg. Kirsten was introduced to the bishop by Angel. Soon after Jeff's suicide Kirsten and the bishop are being haunted by Jeff's spirit. It is foretold that Kirsten will die soon and the bishop soon after. Kirsten's death is inevitable but the bishop's death can be prevented.
As the story goes the bishop does die when he returns to Israel but soon possesses Kirsten's schizophrenic son Bill. Angel has to decide whether all that happened is truth or all just ways to cope with death.
Once again this book is filled with the humor that seems only done by PKD. Many group conversations in which the topic becomes humorous. Like the scene in which Bishop Archer is trying to explain to Bill about faith. Bill suffers not only from Schizophrenia but also from Asperger syndrome, characterized by difficulties in social interaction and by restricted and stereotyped interests and activities, Bill's interests being cars. When the bishop explains that water under the car could be a problem but you don't know what you have to take it in faith that there is a problem until you can discover the truth. At this point Bill goes on explaining that there could be many problems and that it may be oil and not water and that it depends on what kind of car. This goes to the point of absurdity and you just can't help but laugh out loud.
While there is no mention of the VALIS in this book the spiritual journey fits with the VALIS theme. Another aspect is that this is one of those borderline science-fiction books that if written by anyone other than PKD might have been packaged as spiritual fiction (if there is such a category...I guess it would fit in with "The Celestine Prophecy")