Okay, I've now read all 4 books, and the Midnight Sun preview.
Yes, none of the characters really act like typical high school kids. However, in my opinion, none of them seem at all autistic or AS either.
Of course they're fairly nice, she wants you to like her characters. And I suspect her own high school experience wasn't traumatizing, or if it was, she's forgotten that part.
Overall, I liked the books. The writing varried from decent to really good. Yes, the plot is fairly predictible, but it's aimed at younger readers, which pretty much gaurantees things will work out in the end. I'm okay with that.