This is the latest offering from Neal Stephenson.

It's about a MMO called T'Rain that gets infected by a virus called reamde (readme with m and d swapped)
From there the story twists and turns like a twisty turny thing. I stayed up 'till 1 a.m. to finish it on a work day.

Although it's in the Sci Fi section, more of this story is not Sci Fi than is. None the worse for that fact.

First line of the back cover is...
Richard Forthrast, a multi-millionaire marijuana smuggler, has parlayed his wealth into an empire by developing T'Rain, a billion dollar online roll-playing game with legions of fans around the world.