The Resolution in the story is that Coraline has gotten back to her world, and got her parents back and at the end.She tricks the other mothers right hand to fall in to the old well, and she left the key in there too.
I think that the theme of this story is carful what you wish for, because when Coraline wanted a world that was not boring she got one, but it was a trap that the other mother set to steal Coraline's soul.