The Hidden City: (volume I: The Devil's Descent)
Lex was content to keep temping for the Devil indefinitely.
Wait, no. That's not right. She wasn't content. More like resigned. Lex had renounced any sense of hope and surrendered to the drudgery of temping in the Devil's call center for perpetuity, but things changed when a workplace massacre left her next in line for Acting Executive Vice President of the Impending Apocalypse.
Now hers is a delicate balancing act - caught between keeping her job and saving the world - and the only end in sight lies beyond scheming coworkers, corporate villainy, killer cops, a secret world within the walls, and a mysterious band of would-be assassins who won't stop until she's dead.