Philip K. Dick wrote wonderful short stories and novels, but VALIS is not one of them. Don’t waste your time reading VALIS, even though you love several other PKD novels. You’ll find it tedious and unengaging.
There are people out there whose opinions you respect who recommend VALIS for one reason or another. Most of those reasons are not compelling. If you stumble across one that is valid, then fine, go for it if you really want to, just don’t expect to have a great time.
I haven’t tried this yet, but I expect the best thing to do is just to read the Wikipedia article.
Recommendations to Myself 