Game Over by Andrew Klavan

Book 3 of Mindwar Trilogy

Summary: 

This time, there’s no escape from The Realm.

The MindWar Realm is a computerized world created by a deranged terrorist named Kurodar. Built through a link between Kurodar’s mind and a network of supercomputers, The Realm is a pathway through which the madman can project himself into any computer system on the planet.

Twice before, Rick Dial has entered the Realm as a Mind Warrior and come back alive. But now, something has gone terribly wrong. A connection has formed in Rick’s brain that sends him hurtling into The Realm without his consent—and brings the Realm’s monsters into the Real World.

As Kurodar works to turn Rick’s brain to his own purposes, Rick’s waking and sleeping life is ravaged by terrors he never imagined.
Rick knows he has no choice but to face The Realm’s final and most powerful protector. But can Rick destroy MindWar without destroying himself and the people he loves?

Opening Lines: 

The city was empty except for the dead, but the dead were everywhere. Rick saw them staring at him through darkened windows, their jaws slack, their eyes open but lifeless. He saw their bodies lying in the gutters. He saw them sitting slumped at the tables in the outdoor taverns, or lying crumpled in the shop doorways, as if death had found them going out or coming in. He saw the soldiers propped against the courtyard walls, their swords still gripped in their hands, their mouths twisted in an eerie rictus--that fixed grin of slow decay.