The Dark Ones - an urban fantasy novel by Gaja J. Kos

The Dark Ones
http://www.amazon.com/Dark-Ones-Black-Werewolves-Book-ebook/dp/B01CENF9EM

In a world ruled by lethal Slavic immortals, Rose and her pack of Black werewolves are drawn into the beginning of a war as they try to uncover the being behind the mass murder of White werewolves.

Because the nature of the killings obstructs the normal passage of souls, Veles, the sultry lord of the underworld, offers Rose his assistance; the were is left facing not only the new knowledge of the pack's hidden lineage but also her growing fondness for the arrogant god...

To win the war, the pack must ascend to The Dark Ones. But to do so, they must be willing to risk being on the receiving end of the immortal community's wrath.