Yeah, .hack is pretty good. I have yet to get Mutation (the second one), but I have passed the first.
They are just like a 4 disk game, like final fantasy games. You continue on your game from disk one onto the other ones. Just like in FF games, you have to pass the first disk to play on the second disk... They are kinda gipping people that way though... all together that will definatly be the most expensive game I ever buy...