Midnight at Ravenbrook by Sam Burns

Nothing in this world means more to Knox than saving his baby sister from the mess she’s slipped into. Fresh out of prison and staring down her five-figure debt, Knox knows he has to do whatever it takes to keep her safe—and make up for the years he left her alone.
One more job.
One last haul.
Then, they’re getting the hell out of dodge and he’ll see his sister sober again.
But when he hits an old mansion, Knox gets more than he bargained for. The creatures inside are anything but human, and when the job takes a devastating turn, pale Emmanuel offers Knox everything he’s been fighting for.
Knox has always been okay with a little bloodshed, but Emmanuel’s demands push him to his limits . . . and offer him an alluring new gift: eternity.