Here are some good articles and blog posts pertaining to New Adult:
- http://www.usatoday.com/story/happyeverafter/2013/04/24/monica-murphy-second-chance-boyfriend-new-adult/2110489/
- http://www.autumnreview.com/2013/04/why-is-new-adult-so-hot-guest-post-with.html?showComment=1366919495884#c5066341151172851174 Look at me in the comments asking the same question.
- http://www.shelf-awareness.com/issue.html?issue=1979#m19779 Scroll down a bit on this one to find the relevant section.
For what it's worth, I have my opinion but I'm curious what a sampling from the internet will tell me.