In the End by Alexandra Rowland

The Fallen Angel Lucien never expected the world to end. Inconveniently enough, it did. He and Lalael, an angel of the Higher Realm, are abandoned to make their way in what's left of the world.It has changed, however. Uncountable humans have died or vanished, and leftover groups are determined to survive however they can, fighting off new dangers and killing anything they do not understand.But demons were not the only thing released into...