The Haunting In Connecticut is a movie based on the real-life experiences relayed in an hour and half long episode of Discovery Channel's A Haunting series.
Not to say that this movie was terrible - it wasn't terrible. It simply wasn't as scary or as realistic as the Discovery Channel's version (yes, I just said that).
If you are looking for a downright scary first account experience of this story then watch the Discovery Channel version. If you want a story that ties up loose ends and has a happy ending then watch the the Hollywood version.