I've seen Blade Runner a few dozen times and read Do Androids Dream of Electric Sheep a few times and recently re-read it.
I was struck (again?) by the massive differences in the story line and how the book was true to what appear to me to be very "Dickian" themes and motifs.
For example, in Dick books the main character often has a fucked up job. In DADES the main character is not a cop, not even really a detective, his job is to find escaped robots.
His pay is miserably low and his bounty for killing the robots allows him brief shimmering moments into the respectable middle class world of owning a real animal (a sheep) instead of an electric one.
But why animals? DADES is structured around the fake religion of Mercerism which simply doesn't exist in BR. Mercerism is a strange cult that seems to exist for the sole purpose of affirming the "empathetic union" of life forms. Dick gives us a premise that empathy is a uniquely human quality but confounds this apparent assertion with another idea: what if robots could be fooled into believing they were human and themselves developed empathetic responses. Would they be alive?
The playing with the question of who is human and who is an android bubbles and flips back and forth a few times in classical dickian fashion. He doesn't hand us a simple scenario, build tension and release it. He hands us confusion, an apparent problem, another apparent interpretation of that problem and evidence that one or both may be wrong or suspect.
The TYRRELL corporation in the novel is active engaged in the attempt to subvert the VK test. It wants to confound Deckert and engages in some fumbled manipulative effort to confound him. BR has none of this.
In DADES the Pris character and Tyrrell's niece character are suggested as "doubles" of each other. Deckert sleeps with one of them to enable him to kill the other, we are lead to believe, on the advice of another bounty hunter who doesn't exist at all in BR. However this was a trick to make him lose his will to fight designed by the androids themselves! The classic Dick story reversal.
The most telling line in the novel, and the pinnacle of Dick's style, is when one of the run-away androids says something to the effect that "We're actually escaped mental patients from an east coast mental facility. We all suffer from massive loss of affect and this is all a collective delusion." In one line he undercuts the logical premise for every single action and we are left to ponder that this entire story is a meta-hallucination of the mental patients. And Dick takes this line no further, but instead we are dropped back into the sci-fi world of escaped androids and bounty cops.
In DADES there is a parallel android controlled police force that captures Deckert.
In DADES the performing android is not a stripper who has a synthetic snake perform sex acts on her but instead is an opera singer at the SF Opera House. This massively expresses the sentiment alluded to in the novel: the androids want to live real lives - to sing, to perform, to be loved by the public. They don't want to be off-world colony slaves.
Another huge back plot theme in DADES is that the earth has been fucked in a nuclear war and that radiation is a constant problem (thus the off world colonies which in BR have no point for existing). Loneliness and desolation are themes that punctuate DADES with the problem of massive apartments and housings filled with "kibble" - the effects of people long gone.
A strange recurring motif in Dick books is fertility: in the Game Players of Titan it is strong and in DADES lead cod pieces exist to protect fertility. But not just fertility in the sense of "having children" but in the sense of fertility threatened and strained. Fertility lost or nearly lost.
Women occupy an odd role in Dick books. They are definitely male-centric novels and DADES is no exception. Except that the main (male) characters are so pathetic and human that the poorly explored and portrayed female characters don't seem all that bad by comparison. Deckert's wife (who exists not at all in BR) is a mental case herself. The Penfield Mood Organ doesn't exist in BR.
DADES takes place in San Francisco, but BR is set in Los Angeles. In DADES the large buildings are explicitly empty but in BR it is ambiguosly the case.
In DADES the issue of "chicken heads" - people with radiation induced intelligence problems - is overt. It BR it goes away.
Isidore is a "chicken head" and is the one who befriends the androids. "J.F.Sebastian" is the stand in for Isidore and is made into a "genetic designer" instead with "accelerated decrepitute".
I can see how the Isidore/chicken head thing would be politically insensitive.
It is because of Mercerism and the sanctity of all life that the risk of "retiring" a human being is an amazingly huge criminal possibility.
The lack of empathy for other androids by androids is a telling sign, but then reflects on the problem: why doesn't Deckert care about them?
Overall I'd say that Blade Runner, while visually stunning, did almost no justice to the subtle complexity of the novel.