Inbetweeners

An angel and a demon walk into a bar...
It should be the start of a joke, except Emmett and Phoenix loathe each other the moment they meet. Reluctant and mismatched partners they may be, but they've been given a job to do on Earth: persuade the newly dead to move on to wherever they're destined to go.
A friendly word here, a nudge there, all the dead should need is a push in the right direction-but dark forces are working against the pair, and the mission takes a dangerous turn.
From hate at first sight, to toleration, to something more... Except time is running out, and soon Emmett and Phoenix will be torn apart and returned to the worlds from which they came. That's not what they want, and neither is willing to go back without a fight...
.... Because even though they're dead, they've never felt more alive. This is book 3 in the series, but all can be read as standalones.