I find this movement in reading very interesting.
Part of me wonders if this has something to do with the reading levels of us as Americans. Are people starting to read "young adult" literature because they do not feel comfortable reading "adult" literature Now I am by no means saying this is the case for everyone. As I know from class, everyone can read adult literature and still enjoy young adult lit. But I was thinking more people outside of academia, maybe people without any college or with very little.
Maybe people have been corrupted by lifestyle and technology, and now feel that adult lit is too different from who they are and too much to read. It seems to me that what is popular in young adult lit is things that are very big in the media (and not for being controversial). Maybe that is a big reason for this phenomenon.
These are all just thoughts. Maybe literacy and reading level have nothing to do with why young adult lit is such a phenomenon. It could all just be a matter of taste, or something else. It would be hard to come up with statistics on these things unless you did some sort of wide-ranging, scale-upable survey.