I think short stories are were it’s at with PKD – he’s an ideas man and doesn’t really have the writing to sustain novels, although he wrote loads, obviously. All of his shorts are collected and available in about 5 volumes IIRC.
Saying that, I did really enjoy the books he wrote late on where he’s getting a bit frazzled. Valis and The Divine Invasion are brilliantly inventive, but very much in the vein of the Illuminati books – worth picking up if you appreciate that type of fiction / secret history of the world.
ETA I shouldn’t say frazzled really as he was stuggling with mental illness by this time – this comes through strongly in Valis, it’s quite a sad and moving book with a clear autobiographical theme.