While the movie and the book are VERY different beasts, it's not fair to say that the movie does not make sense. There is one logical lapse due to a production screw up, but it's not nonsensical (M. Emmett Walsh tells Deckard there is one more replicant on the loose than there actually is).
And while the movie takes a diametrically opposite view of the replicants than Dick's novel does (Dick viewed them with a kind of horror, the movie is sympathetic to them), the fact that Dick liked and approved the rough cut he saw just before his death should, at least, give pause before declaring it a bad adaptation.
Dick is an incredibly interesting author, so it's kind of sad that Hollywood thinks he's the only SF author that ever lived, as it tends to distract from just how good he actually was.