I'm a massive Philip K. Dick fan and there have been plenty of adaptations of his work. Here's my thoughts on those I've seen, in case you wondered.
A Scanner Darkly based on A Scanner Darkly
Controversially, this is my favourite Philip K. Dick adaptation. Arguably pointless in that it brings little new to the story, it pays the most respect out of all the films based on his work. The bleakness, the paranoia and the characters of the novel have been transferred near-perfectly and large sections of dialogue have been lifted word for word. The rotascoping is a stroke of genius bringing the scramble suit to life and creating a surreal, hypnotic experience that gets the 'feeling' of the novel spot on.
Blade Runner based on Do Androids Dream Of Electric Sheep?
Although Ridley Scott made an absolute classic with Blade Runner, bringing enough to the story to make it is own while keeping its core, I'm too staunch a PKD loyalist to admit this is the best of the adaptations. Too much of the novel was changed for my liking and Harrison Ford isn't the right casting for a true PKD hero, but it's undeniably cinema gold.
Total Recall based on We Can Remember It For You Wholesale
Arnold Schwarzenegger is the antithesis of the PKD character - a paranoid, insecure everyman. Strictly speaking, it's a fairly dire adaptation, but it's a fantastic film in its own right. Verhoeven's trademark violence plays out beautifully and Arnold delivers those one-liners with his usual charisma. 'See you at the party, Richter!'
Minority Report based on The Minority Report
One of the better Spielberg films of the past 10 years, this film is a little too sexy for its own good. Tom Cruise is a bit cool and everything is slick, neatly tied-up and ultimately happy. Good fun with some neat ideas and it's solid in its own right, but it's just too 'Hollywood' for a PKD story.
Screamers based on Second Variety
Critically panned and regarded as being nothing more than a wannabe Blade Runner mixed with The Thing, I have a deep love for Screamers. It's a paranoid, bleak '90s sci-fi with the legendary Peter Weller playing the lead. The ending of the story was changed and it suffers as a result. Not a great film, but for nostalgic purposes, I adore this film.
Paycheck based on Paycheck
The biggest crime with this film is not that it doesn't do PKD's story justice, but that John Woo's career had completely hit rock bottom. Vaguely entertaining but generally stupid.
Next based on The Golden Man
Horrible. Simply horrible.