This Rage of Echoes — Simon Clark

You know the monster's face....

The future looked good for Mason until the night he was attacked...by someone who looked exactly like him. Soon he will understand that something monstrous is happening--something that transforms ordinary people into replicas of him, duplicates driven by irresistible bloodlust.

It's the one in your mirror.

As the body count rises, Mason fights to keep one step ahead of the Echomen, the duplicates who hunt not only him but also his family and friends, and who perform gruesome experiments on their own kind. But the attacks are not as mindless as they seem. The killers have an unimaginable agenda, one straight from a fevered nightmare.