The Demonata Book 2: Demon Thief- By Darren Shan
Kernel Fleck has always known he's weird. He sees lights. Strange, multi-colored patches of light, swirling through the air. But it's not until a window opens into a demon world, with horrific consequences, that Kernel discovers his powers. As a Disciple, his mission is to hunt vicious, powerful demons to the death...
*book has wave to it, but perfectly readable