Second Skin — Caitlin Kittredge

When werewolves from Nocturne City's oldest packs start showing up shot through the head execution-style, police officer Luna Wilder must find out what's killing them and why...before she becomes the next victim.

Luna traces the killings to a band of shapeshifters made of smoke and shadow who drink the blood of their victims for strength. Believed to exist only in legend, their race is all too real--and now their leader, Lucas Kennuka, is out to wrest Luna's heart from her beloved Dmitri. To make matters worse, Dmitri is suffering from a mysterious illness brought on by a demon bite, and his condition grows more grave with each passing day. Now Luna must rely on Lucas to defeat an invisible enemy--a serial were-killer bringing death and destruction to all who stand in its path...