Graveyard Shift (Lana Harvey, Reapers Inc., book 1)
From the publisher:
Lana Harvey is a reaper, and a lousy one at that. She resides in Limbo City, the modern capital of the collective afterlives, where she likes to stick it to the man (the legendary Grim Reaper himself) by harvesting the bare minimum of souls required of her. She’d much rather be hanging out with Gabriel, her favorite archangel, at Purgatory Lounge. But when a shocking promotion falls in Lana’s lap, she learns something that could unravel the very fabric of Eternity. If the job isn’t completed, there could be some real hell to pay.