Can't add much more than what you all said. Joe really does give us such sharp visuals. You know how they say to writers, show, don't tell? Joe does both. He tells and backs it up with such vivid descriptions.
The kidnapped child is horror. The absolute fear of that for the child and for the parents/family/friends. One minute someone is there and then they are just wiped off the map. So many missing people out there. I can't even imagine, I don't want to imagine being the victim or the family searching.
Some might say Finney was hallucinating from hunger and cold -- but I believe that black phone rang. I believe that the kid on the other end was the last victim. And I embrace the idea of a ghost support group empowering the next victim to attain retribution. I imagine as each child was put in that basement and died, that black phone became a party line to the next kid.
This is what Joe's writing does. It inspires a person to think of the vast possibilities beyond his story.