Clif
PKD is a minefield, lots of weird trash in there which is still fun if you just feel like a PKD book and have read the gems, but it's easy to get thrown off if you pick up one of the more throwaway ones.. outside of Scanner Darkly which is my favourite that you've already read i really love these:
A Maze of Death -- i think Mark Fisher writes a bit about it in the weird and eerie, very paranoid sci-fi with multiple characters trying to deal with a botched expedition to a new planet
VALIS-- more great paranoid 70s California stuff if you liked Scanner Darkly, though a bit more dense on the sci-fi elements from memory
Ubik -- I feel like this is the cult hit? Or the one I hear cited most often as a favourite. Likewise, feels in a similar world to VALIS
Man in the High Castle -- less sci-fi and more speculative, I really really liked the read but remember it being a bit clumsy at times, an alt-history where the Nazis and Japanese won WWII and divided up the US accordingly. a lot rides on the premise obviously, but there's a lot to like
Confessions of a Crap Artist -- bit of a deep cut and his only non sci-fi novel. i don't think many people like it, but i only read it recently and was surprised to enjoy it... maybe cos it felt like a shame he got pigeonholed when he was desperate to write something outside of the sci-fi realm. in saying that... when i got bored i just pictured it as a sci-fi with the paranoid characters being right and that helped.. i feel like for lots of PKD books i kinda imagine a better book to get through it if that makes sense? not very convincing i know!
hard to say what to avoid cos there's so many different styles in his bibliography that some will like the stuff others will hate. Clans of the Alphane Moon sucked ass is all i remember clearly!