just finished. IMO, prob one of the best adaptions of a King story. I guess when you work without the time constraints movies have, you can fully explore all the characters and not leave that much out.
as to the boys, this was, if you will, a call back to his book Desperation where the demon was in a cave that collapsed in arizona which trapped a group of Chinese miners. Also there are similar references in Desperation where the demon feeds off of humans and its appetite grows exponentially to the point the human body breaks down and it must move to a new host. El Cuco had similar characteristics