|EuroGamer shares its impressions from the 1st '.hack' episode in this article right here.
Here's a bit from the intro:
There aren't a lot of games around these days which can be described as "high concept", but once we'd got our head around the basic idea behind .hack//INFECTION - the first of four consecutive volumes in the .hack story, and it's pronounced "dot hack slash infection" if you're wondering - we were convinced that we'd found one. It's not often, after all, that you get your hands on a game where your little on-screen pal is playing a videogame. A massively multiplayer online videogame at that, although in fact .hack is resolutely single-player and there's not a network adapter in sight.