This book is on pre-order until book delivery arrives. 
 
The Devouring by AM Shilling:
 
Throughout their marriage, Jason and Ayana’s lives always ran parallel but never entwined. It’s the perfect arrangement. He’s free to pursue his dangerous yet lucrative career as an elite assassin, and she can focus on conducting autopsies for the city’s forensic center.

But after Jason spares a witness to his latest murder, he becomes the prime suspect in his own brother’s homicide. While he hunts for the real killer, Ayana discovers an impossible illness in one of her cadavers. The couple quickly identify an unsettling connection between the two events—one steeped in religious fanaticism and occult conspiracy.

Jason and Ayana must learn to work together, using their wits, lies, and criminal connections to uncover the truth behind a mysterious cult and exact revenge. But human enemies are the least of their concern. Beyond the boundary of their world exists a cosmic threat of apocalyptic proportions, and it is trying to break through.