I did summarise it elsewhere, but I will do it here again.
The original Japanese 'Ring' had a premise as follows:
It is about a rumour that there is a video tape which, if watched, means that the viewer will die exactly a week later- and near the start of the film several students die in mysterious circumstances having reportedly seen said tape.
A young film student decides to investigate this rumour, theorising a serial killer is the reasoning behind it. Needless to say her invesitgations are a bad idea, and from the moment she sees the video onwards things get worse, and worse, and worse as the film ticks by day by day to her apparently inevitable death. She enlists the help of her ex-lover to try and unravel the secret behind the tape, which is very obviously rather supernatural, and it soon becomes clear that both main characters are not exactly normal either- and CERTAINLY not their young son.
The film is rather brilliant in the way it starts mundane and gets continuously more and more evil and oppressive, though once the main secrets are blown it ambles a bit until the conclusion which is rather intense.
It is VERY creepy, especially the video itself (which is nothing like how the rumours describe- the rumours say a woman points at the screen and says "You will die in one week!", but it is actually WAY more freaky than that!), and like I say, best watched late at night in the dark, not because it is directly scary but because of the deep feeling of unease it gives. The video is rarely seen and the power of the images in it is great.
The film spawned a sequel, which was interesting but not very good, and a prequel, Ring Zero, that I have not seen.
Now, as far as I know, the American version is relatively faithful (though the importance of a volcano in the original will probably have to be twiddled- rather more common in Japan!). One difference is in the meaning of the title- in the original I was hard-pressed to understand why it was called Ring, except for the fact that those who are going to die also receive a phone call, hence the 'Ring'. A bit vague, though (though the phone call, like the video, freaked the heck out of me...).
This time, I believe the tagline is that you see 'The Ring' before you die, so more direct this time.
Anyway, I can highly recommend the original, which is fully available on DVD (it's popularity in the west is WHY they are doing a re-make).