The Perfect Assassin: Book 1 in the Chronicles of Ghadid by K. A. Doore
The assassins of Ghadid serve a higher power, dispensing justice in the shadows. Or so Amastan has been taught. Until, unexpectedly, Amastan finds the body of a very important drum chief. Until, impossibly, fellow assassins are being killed off. Until, inevitably, Amastan is ordered to solve these murders. Even worse, the jaan of the murdered start roaming the dusty streets of Ghadid: restless spirits seeking any body to possess. Time is running short, and Amastan must find this perfect assassin or become their next target.