Bird Box by Josh Malerman
Malorie didn't believe there was something out there at first. Her sister tried to warn her. Incidents of suicide and madness were popping up around the world but nothing close to home. Until their parents stopped answering the phone. Then there were cases occurring in their city. Finally, pregnant and scared, Malorie finds her sister in the bathroom in a pool of blood. Thus starts a frightening tale of unknowns and survival.