Graveyard Waltz by Jessie Thomas

Looks like I’ve made some new enemies.

My sister Ellie and I aren’t on speaking terms, someone’s trying to put a stake through Nate’s chest—which is my problem now, because I’m pretty fond of his cold, dead heart—and our latest threat is leaving decomposed bodies on the steps of churches around the city.
So, I mean, it’s your basic paranormal nightmare. Except this time it feels weirdly personal.
As Buffalo’s vampires converge on Caligari Manor for the largest ball in half a century and dangerous outside forces close in, Nate and I discover that our future might be even stranger than the present.
If this night isn’t our last.