Changeling (The Year King)

Book 2 of the Year King. Since discovering her former flatmate Demi is a runaway fairy king, Ivy's gotten used to having friends who aren't visible to normal people. She's working a usual job, living in a normal flat, and trying to keep her life as weirdness-free as possible. Mostly, that means trying not to think about the Enemy, its upcoming visit, or the fact that Demi has less than a year to live. When a woman dressed like the Enemy shows up in Ivy's flat seven months early, Ivy sees a chance to finally put an end to the Enemy's deadly appearances-until the woman herself burns to death in the street.

A three-hundred-year-old serial killer is changing its tactics, and strangers are showing up in Dublin looking for the source of a world-altering catastrophe that's somehow connected to Ivy-and to the Enemy itself. As Ivy investigates the origins of past murders and future disasters, it's becoming clear that the Enemy's next target might be Ivy herself.