O Carniceiro do Pântano (Capa mole)

The book's unsettling mood really drew me in, but I wonder if the author based it on real events or purely from imagination. How did the setting influence the horror elements?

The lines between right and wrong blurred so effectively that I was constantly questioning my sympathies. Was this intentional to reflect the complexity of the characters?

The suspense built up so well through the shifting perspectives and timelines. I'm curious whether this structure was mapped out early or developed as the story unfolded.