Love, Laugh, Lich by Kate Prior

Some people have monsters for a boss, but not everyone has an undead Necromancer Lord at the office.
Lily has been the Lich’s secretary ever since his evilness took over the company. She loves her job, but she’s got some questions about her boss. Like what’s under that cloak of ever-billowing.
Her wondering intensifies when one day the Lich needs something from her that isn’t just scheduling appointments– but a shiver. He needs it for a spell, but it feels like it crosses a line from their usual workplace banter.
After her contributions to his dark rituals become more than OSHA compliant, sex-magic-and-triple-cocks-oh-my, she starts to contemplate whether the Lich Lord returns her feelings, or still only sees her as his secretary. Lily may have given him her body, but he never asked for her heart.