This novel has a religious basis. People have refered to this as an 'LSD', or 'wildly disorientating' novel, but that is simply not the case. I guess many people don't really understand what PKD is getting at. This book deals with God and Satan, as well as the phenomenon of the wine into blood thing, ontology etc. I'm not qualified to discuss these issues, but it must be said that they were of profound importance to PKD.
As a SF novel, 3 Stigmata is absolutely brilliant. The ideas in this book are enough to ensure its brilliance alone; like Perky Pat and Can-D (which I felt was sheer genius on PKD's part), the hovels on Mars, the extreme temperatures on Earth (although this gets little attention as the book progresses), E-therapy, and of course Palmer Eldritch himself and Chew-Z. The time-travelling as a result of Chew-Z provides some of the best moments in the book, and the ending, where Barney and Palmer Eldritch merge into one... well, this defies words.
If anything is flawed in this book I believe it is the characterisation. In PKD's best books you feel strong empathy for the characters, good and bad (a prime example of this is Ubik.) Aside from Palmer Eldritch himself, who is a brilliant character, the chars. are not PKD's best. Barney, Leo, Roni, Emily are half the people Glen Runciter and Joe Chip are.
This is not my favourite PKD novel, but that is due to the subject material, not the execution of the novel. '3 Stigmata' is the first really religious PKD novel, and it stands as a precursor to later works such as 'Valis' and the 'Divine Invasion.'