Infinite Reality — Peter Meredith

A hundred million on-line players with thousands of choices, but everyone knows there's only one game: Infinite Reality. When a judge declares it a monopoly, the co-creators become competitors and then very quickly become murder victims with one thing in common: they were all online when they died. Everything points to the sole-surviving creator, Atticus Arching. When the FBI can't find Arching in the real world, they send Agent Daniel Roan and his team to the “other side” to track him down, only to find out that the game is more than just a game and Arching is more than just a computer programmer. He's the most dangerous person in two worlds and can kill in both.