Deep State — Walter Jon Williams

By day Dagmar Shaw orchestrates vast games with millions of players spanning continents. By night, she tries to forget the sound of a city collapsing in flames around her. She tries to forget the faces of her friends as they died in front of her. She tries to forget the blood on her own hands.

But then an old friend approaches Dagmar with a project. The project he pitches is so insane and so ambitious, she can't possibly say no. But this new venture will lead her from the world of alternate-reality gaming to one even more complex. A world in which the players are soldiers and spies and the name of the game is survival.