The second book in the urban fantasy series, Armageddon Angels, by Eric Swett (innocenteric).

Apocalypse Rising: The Coming Darkness is an Urban Fantasy about a fallen Angel named Justin. He just happens to be one of the Horsemen of the Apocalypse, the Grim Reaper himself, Death. A year has passed since he remembered who he was and what he is. He is regaining some of the abilities and memories he lost when he chose to fall to earth and live amongst humans, but he has a long way to go before he can fully reclaim his title. When Justin comes across a young girl being chased by a monster, he does what he can to save her, but he soon discovers this is no normal girl, and failing to save her will change the world forever.