Well, yes, but I'm not just talking about //roots or the game series. The .hack project encompasses a vast storyline by using various formats like games, manga and anime, based on the game "The World", which seized the gaming market in the early 2000s after a computer virus named Pluto's kiss wiped out all operating systems but the one The World runs on, Altimit OS.
It started with the anime .hack//sign, then went into the game series (.hack//infection, .hack//mutation, .hack//outbreak, and .hack//quarantine). I missed that game series too, but I plan on playing the new ones based on //roots. =3 On two side stories, four people try to find out what is causing all the comas during game play in .hack//liminality, while in .hack//legend of the twilight follows two characters that win a contest and get chibified characters.
There were also various books and card games based on the series.
Then, according to the .hack storyline, the CC-Corp building caught fire and The World had to be remade into The World R:2, which quickly became a cesspool of player killers. That's where .hack//roots (which I agree, it had a nice storyline~) took off, and the newest game series, .hack//g.u. (which will run 3 volumes long, Rebirth is already out and another is coming out this year), is based on the events of //roots.
Wow, I just scared myself. Though, it's not an obsession, I swear.