This is my least favorite book of all four. But it is not unimportant to the series.
New Moon is a book of many twist. A heart-break, a love triangle will begin, a new mystical creature will be introduced(will it be a foe or a friend?) and a new...complication?. There is little Edward-Bella love story in this one which is probably why it is my least favorite of all but all the same it is a fantastic book and wouldn't dream of missing it.
It's a little slow-paced but I think it worked best for the mood of the story.