I remember, back in 1995, when K. W. Jeter began a new series of books (three in all, eventually) that were sequels to both Philip K. Dick's Do Androids Dream of Electric Sheep? and the movie version of that book, 1982's Blade Runner.
Of course, up until a few weeks ago, I had not read the novel by Dick (and that reading was precipitated by me seeing the film again). But knowing that Jeter (a long-time friend of the late author) had been authorized by Dick's Estate to continue the themes presented in both the 1968 book and the film, after I actually got done with Androids, I checked out this book at the library.
Beginning several months after the events of the film, Deckard has retired to an isolated shack outside the city, taking the replicant Rachael with him in a Tyrell transport container, which slows down the replicant aging process. He is approached by a woman who explains she is Sarah Tyrell, niece of Eldon Tyrell, heiress to the entire Tyrell Corporation and the human template for the Rachael replicant. She asks Deckard to hunt down the "missing" sixth replicant. At the same time, the human template for Roy Batty hires Dave Holden, the blade runner attacked by Leon, to help him hunt down the man he believes is the sixth replicant - Deckard. Deckard and Holden's investigations lead them to re-visit Sebastian, Bryant, and John Isidore (from the book), learning more about the nature of the blade runners and the replicants. When Deckard, Batty, and Holden finally clash, Batty's inhuman fighting prowess leads Holden to believe he has been duped all along and that Batty is, and always was, the sixth replicant.
I give kudos to Jeter for trying to meld the two media products together, but to be honest, instead of creating a new narrative, the author spends way too much time creating one contrivance after another, shoehorning plot points in like Mary Shelly's Doctor Frankenstein in some desperate attempt not to fully admit that the book and the movie are really two different visions of same story and should be treated that way.
My understanding is the conspiracy theme Jeter pulls out (someone is out to end the reign of the blade runners) is more or less designed to cover plot holes that have been identified by fans of original movie -such as Leon's ability to bring a gun into the Tyrell building, or the reference to the sixth replicant. Also, the character of Sebastian died in the movie, yet he is alive in this sequel. Pris was clearly stated as being a replicant in both the movie and the original novel, yet in Jeter's story he claims she was human. Pris was clearly destroyed by Deckard in both the movie and the original novel and that Sebastian has the ability to bring Pris back to life as a replicant unwittingly introduces numerous problems: the book implies that Sebastian somehow was able to do this without realizing that her original body was human. It is likewise unclear why Deckard would have left her, or any suspected replicant he retired, in a state from which they could be repaired.
The book does rely too heavily on the film more than the original tome, which clearly indicates that the folks behind this continuation thought that audience who would read this novel would feel more comfortable if this new series monkeyed Ridley Scott's take than Philip K. Dick's one. But to be honest, the only ones who might've read this were the hardcore fans of the original tale (and not, I think, the movie -which is a completely different fan base). But they would be disappointed to find how much Edge of Human is not really a Dick story.
Which is a shame really, because Dick's story was so good.
In the end, this book was constructed like sequel to a movie and a novel that never intended to have a sequels. In Jeter's attempt to explain the plot holes of both, it reads too much like fan-fiction, ala Star Trek; he spends way too much time creating an overly complicated tale of conspiracy, lies and deceit and then smashes us over the head with those ideas to drive home his point that he is trying to fill in all the blanks. It is then that you eventually realize why there's never been a movie sequel to Blade Runner -because it's just too complicated to move the story further- plus, more importantly, why the estate of Philip K Dick should've just left well enough alone.