Silver Mirrors: An Apparatus Infernum Novel
A. A. Aguirre

Criminal Investigation Division inspectors Janus Mikani and Celeste Ritsuko were lucky to make it out of their last mission alive. 

Since then, strange troubles have plagued the city of steam and shadows, apparently as a result of magic released during the CID inspectors' interruption of an ancient ritual. The fabric of the world has been unsettled, and Mikani and Ritsuko must investigate.