A Shadow Bright and Burning by Jessica Cluess

What happens when you create a story set in an alternate Victorian London beset by a group of demons known as the Ancients, think Lovecraftian creatures, add in some sorcerers and magicians along with the darker side of the Fae, and give readers a feisty heroine who is "the prophesied one" only - she may just not be, and you have the makings of an exciting new YA fantasy series with plenty of twists!