These days so much other media has been influenced by it that it doesn't look nearly as original.
But just imagine reading it when there were no books or movies about:
- cyberspace inhabited by AIs
- neural interfaces
- corporate armies
- insanely rich people living in Earth orbit
- genetically engineered assassins with body augmentations
- slum-dwelling hackers who break in to corporate data stores
Neuromancer brought all this and more in to popular consciousness in a blinding flash.
After Neuromancer, Gibson came out with Count Zero (which I liked even more than Neuromancer itself) and Mona Lisa Overdrive (which wasn't nearly as good as either of the books that preceded it). I stopped reading Gibson after that.