Set in a dreary, slow-burn atmosphere dominated by uncanny analog horror. Aside from the plot's originality, I was most captivated by its trenchanly biting score accompanying the few "jump scares" --assuming they can be categorized as such. I also liked the protagonists' investigative efforts as they traversed the unknown in pursuit of salvation.
Another considerable point is the preservation of mystery, the effect of which remained steadfast through to the ending; the source of the tape, along with Sadako's details and abilities, remain obscure.
Overall, this is a staggeringly impressive feat for its time and--as is routinely brought up--ends with a brutal, unforeseen plot twist.