Dagger Dark by Richard Millership

New York City in the year 2018 is a decaying fortress where serial killings are so commonplace they barely raise an eyebrow. A designer-drug culture where everything is legal – except for those substances so dangerous even knowledge of their existence is controlled. Substances like Dagametoxamine, or Dagger. Then comes a series of murders that turn even the hardest of stomachs, their signature so grisly it seems impossible the perpetrator is human. But these killings foreshadow a greater threat: the possibility that Dagger, capable of turning angels into demons, is working its way into the ecosystem. ISBN 9781863306188.