Spiral, by Koji Suzuki

Mitsuo Ando works as a pathologist and has performed hundreds of autopsies. When the body of an old school friend by the name of Ryuji Takamara arrives on his table, Ando unexplainably feels like the body is trying to send him a message. Ando’s personal problems have rendered him lonely and nearly friendless, and he soon finds himself becoming obsessive in a search for an explanation of Ryuji’s death. As he hunts for an answer he discovers more strange deaths - and a bizarre story which attribute them to a videotape that can kill…
Sequel to the massively influential novel RING. Far from sticking to the basic ideas of that first book, Suzuki flies off into even more bizarre territory of the weird and wonderful. Mainly the weird. If you found the idea of a videotape that can kill hard to swallow, then you better stay away from SPIRAL.