FFabian. I also wonder this when I see a novel is for YA. However since I read The Hunger Games which I found exceptionally good (for being a YA novel) I have been more open to trying them. My biggest dislike is when there is a significant high school-esque romance occurring between the main character and another character. This is a huge detractor for me because often times the moments are written in a very superficial "oh my god he is like so hot I want to jump his bones" manner. (This happened to me just recently when I purchased another YA novel that had a unique story I thought was interesting).
I'll have to give the free chapters a preview and see!