What is the most frightening book you have read in the horror genre?

@DearAmbellina2113 What’s it about?

@SW-User An ancient demon emerges from the earth and possesses the body of a huge sheriff. The thing that made it so terrifying was that it was such an ancient evil that it had existed long before the demons of the Bible, and because it took control of an authority figure (who happened to be physically huge), it was able to abduct a lot of people because we're programmed to obey authority figures and trust cops. But what happens when the guy you're supposed to trust who holds all the power is EVIL? It really explores the primal fear of isolation and helplessness.