This is Not a Game

I recently finished reading This is Not a Game by Walter Jon Williams.
This was a really good read, blending a few of my favourite subjects. Dagmar is an alternate reality game designer, and this book follows her story as she builds up the game and garners more and more participants to the action. Obviously with this sort of story, the line between what is real and a game becomes blurred, but the story is so much more than that. There's some really cool software involved!
This isn't set too far in the future, in fact, could be set within a few years, which makes it just a little scary. The action is well paced and the characters are really interesting.
I thoroughly enjoyed it.