A Sin of Choice by Noah Harris

Azrael and Tobias made their choice, and their choice was one another. The former angel and his mortal lover denied the very laws of Heaven set before them and took to the open road to escape judgement and prying eyes. Along the way they will find there is plenty left in the world to gaze upon in wonder, and in Tobias’ case, a few demons of his own to face. Their escape will turn into a journey of discovery and adventure, leading them down a path they could never have anticipated.
Meanwhile, Heaven finds itself in turmoil. Odd events are happening across various realms, and Gabriel and Raphael are frantic to recover their lost charges. Even as they scramble to find their wayward brother and the mortal, others maneuver around them, keeping Azrael and Tobias out of their grasp. Events that were set in motion years before are rolling forward, with Tobias and Azrael at the center of it all. All will play a part, and Tobias and Azrael will have to face the consequences of their choices.