This one is different, though. There are two main characters: Nicholas Brady, who receives messages from aliens telling him what to do; and Phil, his science fiction writer friend he bounces theories off. Phil is the sane one, Nicholas is batshit crazy. Aliens talk to him through the radio, the soviets send him coded messages in shoe adverts. Or maybe he's not. The aliens also cure his son's birth defect and help him recover from a car accident quickly.
Nicholas and Phil could well be the same person, and read this way the novel is a glimpse into the mind of someone with mental illness. He hears voices, creates theories to explain what to him seems frighteningly real. It becomes difficult to separate the real events from those that may only exist in his mind. Phil K. Dick had a history of mental illness, and this is his attempt to convey what that is like.
Or it could just be a story of aliens and their attempts to depose a tyrannical president of the United States. In which case, the events are all real. There's also a neat parallel drawn between mental illness and religion. Is there any real difference between believing in a benevolent alien talking to us from a satellite and believing in an invisible, benevolent sky father that tells us all to be nice to each other?