The Gathering by C. J. Tudor was a thriller with heavy horror vibes that I was immediately sucked into.

The overall atmosphere was one of a heavy horror influence a la your old school vampire (vampyr in this novel) stories where they are vicious blood suckers, and something to be feared. But on top of this there is the focus more on a story of a thriller-like nature, with the horror aspect being more of a world-building tool than actual horror-esque events taking place (such as serial murders and the note of constant fear to the story).