Fountain of Knowledge

There is occasionally sex in YA -- I'm thinking John Green's Looking for Alaska, Laurie Halse Anderson's Speak, Chris Lynch's Inexcusable, and probably a few others. It isn't common, but it does happen in YA books aimed clearly at older teenagers.

Additionally, it is the quickest way for a school library to ban your book, as happened with all three of the above.

Otherwise, I think Michael's sense is pretty good. There are variations within YA in language, even in narration of third person stories, but for the most part they are close to adult books in storytelling, just not in voice of internal dialogue and similar. For instance, there are experimental and literary YA novels. There are none in middle grade.

(There are some in both groups of prose poetry, but I don't count that as experimental or literary for these groups, since that style has been acceptable for decades in stories for children and teens.)

Lorien