Coraline?

I found the story Coraline to be a very strange story and a few days later I realized the animated movie Coraline was the same story. I never watched the movie, but I believe I should do so to get a better understanding of this short story. Coraline is an adventurous girl and she calls herself an explorer, but what is the concept of the hidden room that Coraline stumbles upon? And why does she have a second set of parents? Everything is parallel to her real life, but things seem very off and have hidden secrets. I don't think the story was clear through the comic, but after all it was based on a much more detailed novel. Since the novel was made into a movie and the movie got high ratings the story must be far more interesting than what I'm getting from it.