It's not for everyone, but it's truly a unique RPG experience.
Anyways.... .hack (yep you pronounce the dot in front of it-- dot hack) is truly an interesting game idea... its a simulated MMORPG, I suppose being the best way to describe it.
You play as a kid, who's playing an online game, where he interacts with other characters and things like that. At the beginning of the game, you play with one of your school friends, named Yasuhiko. He has a character named Orca, and is the second-most powerful character in the entire game. The most powerful is another character, named Balmung.
You go into a dungeon, because he's teaching you how to play the game. However, the boss in the dungeon is something out of the ordinary. He has a red staff, and points it at Orca, and Orca's data is drained. He's about to come after you, but something or other makes you wake up somewhere else. In real life, you find out that the guy who was playing as Orca, your friend Yasuhiko, went into a coma.
Later on, you find an item called the "Book of the Twilight" and it creates a bracelet on you that allows you to drain data from monsters, just like that boss you saw before. So, you are believed by many to be a hacker. Well, actually you are a hacker. Yay! You hack into numerous gates and into servers that are closed down, in order to learn more about what happened to Yasuhiko and what happened to other people as well.
This game is rather clever, but sadly, that appears to be all it has. Nothing that great, even for RPGers, and MMORPGers will just spit at the screen and say "what the hell is this crap?!" Only the true fans of .hack will really appreciate this game, and get the most out of it, so be warned gamers.