The thing to understand about VALIS is that it's an adaptation of his own experiences. i.e., the events of 2-3-74 actually happened to PKD. He then fictionalize

The thing to understand about VALIS is that it's an adaptation of his own experiences. i.e., the events of 2-3-74 actually happened to PKD. He then fictionalizes a lot of the aspects around it (especially in the second half), but all the philosophical musings are things he actually struggled with in real life. PKD likely suffered from a large variety of mental illnesses, and he frequently wondered if he was schizophrenic himself (although he had therapists give him a negative diagnosis). The events of 2-3-74 may have also been the result of a frontal lobe epilepsy. He constantly was trying to figure out whether the things he experienced were the result of mental illness or something else entirely. Or trying to figure out whether there's any difference at all. The core theme of his work is "what is real?", and that became something that consumed his own personal reality in his last decade of life. So I think a good way to read VALIS is knowing it's coming from a person who was deeply suffering, and trying to come to some explanation of what he experienced. And how that truly underlies Horselover Fat's deep fear that the universe is possibly guided by an "irrational mind". PKD wanted to know whether his suffering had any meaning, or was just the result of an irrational, and unknowable universe.