Valis, by Philip K. Dick

Valis - Vast, Active, Living, Intelligent, System, Philip K. Dick's gnostic vision of one aspect of God. Valis is the first part of the VALIS trilogy.
It's probably one of the most personal books he wrote. It's based on a personal experience that happened to Dick in March 1974. The main character in the book is only mentioned by the name Horselover Fat, which is a wordplay with the authors name. "Horselover" is English for the Greek word philippos. "Fat" is English for the German word dick.

The story begins with the suicide attempt of Horselover Fat's friend Gloria. It's told in a third-person point of view at first. But almost immediately, the reader is interrupted by the main character saying, straight to the reader; "I am Horselover Fat, and I am telling this in the third person to gain much-needed objectivity.". This makes the story more "real". It's not just a non-person, telling the story in third-person, it's the main character himself. Dick uses similar little "tricks" later in the novel to push the reader further down the spiral of his delusional mind.

Horselover's friend eventually commit suicide,  which is the start of  Dick's (Horselover Fat's if you want) story about what happened to him. The whole book is surprisingly sane and "normal" through half of the book. The familiar PKD spirit (abstract delusional mind-fuck) takes form only in the second half. It grabs the reader slowly, step by step.

The whole book is basically about Horselover's inner (effected by outer events though) search for the truth, and the search for God (if there is such an entity). It isn't really much of a search though, as Horselover have real contact with Valis (Vast, Active, Living, Intelligent, System. Read: God. Or Extra Terrestrials if that's your cup of tea.), halfway through the book. Valis takes form as a pink beam of light, which holds all information man ever wanted.
Philip K. Dick's way of writing makes the reader believe in Horselover's words, even though he admits that he's insane.       About this time two new prepositions entered Fat's mind, due to this particular conversation.

      1. Some of those in power are insane.

      2. And they are right.

     By 'right' read 'in touch with reality'... The psychiatrist in charge of treating him for his lunacy               _   had ratified it. Now Fat would never depart from faith.
Page 63

Dick makes us accept Fat's claims simply by stating them as fact, and always having other characters either accepting or rejecting Fat's claims.
Dick also uses the old method of the Big Lie; If you give the readers a lie which defies all probability, and is big enough, and they accept it - you can fit in lots of little lies in under it with no problem at all. In this case the Big Lie (or is it Truth?) is the central event of the book - the "pink beam of light" a.k.a Valis. By the time the three-eyed aliens from Sirius are introduced, we've already accepted the big lie(/truth), therefor we accept them without hesitation.

Valis holds much more interesting philosophical thoughts than I can describe in this analysis, it's much more deeper than I can describe. You have to read it yourself to fully understand. And even then, you wouldn't understand. At least I don't. And I ...