A Demon In My View by Ruth Rendell

The book revolves around a reclusive, socially awkward man who secretly harbors a dark fascination with death and has a history of committing murders. He lives in a boarding house, where he keeps a mannequin that he treats as if it were a real person, a chilling reflection of his disturbed psyche. His life becomes increasingly complicated when a new tenant moves in, setting off a chain of events that threatens to expose his sinister past. As the tension escalates, the man struggles to maintain his facade of normalcy while his inner demons and the threat of discovery loom over him. The 5677th greatest book of all time