Sam Linnifer Series by Catherine Webb

Sam Linnifer works part-time at a London university as a translator of obscure ancient texts. He's a quiet fellow with a few friends and an affection for cats. He's also immortal and the Son of Time. You might know him better as Lucifer, the Devourer of Souls, or the Devil. And with all the gods in Heaven about to go to war over the ownership of Earth, you're going to be extremely glad he's not exactly who legend makes him out to be.

With the aid of the Pandora Spirits, the elder Gods have taken a giant step toward freeing the dread Lord Cronus. It seems that Earth's only hope rests with Sam Linnifer and the power of the Light bestowed upon him by Time. But unleashing the Light would have deadly consequences for Sam. For to do so, he must touch the mind of every human on Earth. And to save their souls, he may have to destroy himself. This is the stunning sequel to Waywalkers.