Exegesis - a 2011 edited selection of Philip K Dick's diary from the last eight years of his life (between 1974 and 1982) - has become a key text for me. Although I had never looked at it until last autumn, Exegesis is one of only three works that I have in threefold: as paper copy, Kindle and audiobook (the others are Hobbit/ Lord of the Rings, and Jonathan Strange and Mr Norrell).
The great value for me has been stimulation: I find Exegesis to be energising and enthusing. Indeed; it helped dig me out from a spell of directionless demotivation - so I feel gratitude toward it.
A fair bit of it is also very interesting and enlightening; although ultimately I regard most of it as wrong (after all, I live in a minority of one). Nonetheless this does not trouble me in the slightest. Exegesis is such an honest work - so raw and energetic, intelligent and exploratory in its genuine philosophising, that this is all to the good.
Consequently; I have also gone back and re-read the PKD novels that I encountered in the middle 1980s; and read several others (or else listened as audiobooks). One of his novels - Valis - was published in 1978, in the middle of the Exegesis period, and using many of the events and ideas from that book. Indeed, most PKD fans read Exegesis through the lens of Valis.
Valis is a work of art, rather than a collection of notes - and some find it PKD's best novel. But I find Valis much less valuable than Exegesis, because it strikes me as less honest. The philosophical fireworks are presented through the screen of a skeptical, indeed cynical, narrator - and in a distanced, ironic fashion. Whereas from Exegesis I 'know' that these were of burning and urgent significance, at the time they happened; with Vlais the ideas seem (and are) secondhand.
Likewise the lectures and essays of that period - such as "How to build a universe that doesn't fall apart two days later". In making this speech/ essay for public consumption; PKD distanced himself from the daily (nightly) reality of his thinking; made it fit into a schema - which in real life, it never did.
Therefore, while I fully realise that Exegesis would not appeal at all to most people (indeed, I am surprised anybody except me finds it worth reading!) I regard it as without doubt the best thing of PKD's later years.
This is also because I find that all of PKD's very best novels - by my estimation - to have been published in a brief period of just five years between The Man in the High Castle of 1961 and Do Androids Dream of Electric Sheep in 1966. There were indeed seventeen novels (!) published in these years - but the best I have read (and I haven't read them all) are Dr Bloodmoney, The Three Stigmata of Palmar Eldritch, and The Penultimate Truth.
The earlier novels I have sampled are rather poorly written and did not keep my attention; the later novels are sometimes very good in parts (e.g. Ubik, Maze of death, Flow my tears) but do not satisfy as a whole.
My conclusion is that Dick's central and dominating preoccupation moved from fiction to philosophy as he got older; and the type of unsystematic philosophy he did (or rather lived) was unpublishable at that time; although in more recent years he might well have blogged it - much as I do. As a young man, therefore, PKD thought via stories; as a middle aged man he thought via philosophy.
To make a living, the older PKD repackaged his philosophy into novels, stories, speeches, essays - but these were secondary to the solitaary, self-addressed reflections that are sampled by Exegesis. And when he tried to 'use' these primary notes as source material; the need to be systematic, the need to distance himself from the embarrassing honesty and rawness of the original, the attempt to justify and persuade others... all these requirements got in the way, and diminished the quality; while at the same time creating work that admittedly some fans regard as his best.
Thus Ubik, A Scanner Darkly or Valis are often asserted to be the peak of PKD's achievement - and for some people this presumably is the case. But not for me. I regard these as hybrid works, somewhat contrived and unspontaneous, and never fully successful.
PKD worked best when he worked fast (very fast) - both as a fiction writer (staying awake for several consecutive days of solid typing, using amphetamines); and also as a philosopher: sometimes generating many thousands of words of Exegesis in marathon nocturnal sessions.
Certainly not a healthy life: and not a healthy man - but I am grateful for his achievement.