Natalie J. Case 
In Gathering Shade [EPUB ebook] 

Held captive by the fanatical 8th Battalion, Mason Jerah is convinced he doesn’t have long to live… and he isn’t alone in his captivity. The Shadows have a plan; one that could mean freedom.
Meanwhile, operative Raven Ivany struggles against the forces aligning against Shades and Shadows — Shifters and Sages — and finds an unlikely companion in Zero, a teenage girl with a mysterious past and desire to prove herself.