Is Quality Fiction a Victim of Declining Attention Spans?

I’ve written several posts in the past about Young Adult (YA) fiction, not because I have any interest in it per-se, but rather because it is apparently about the only genre where sales are actually increasing. And this is at least in part because it is popular with adults as well as with the target audience. 

What is behind the trend, one wonders? Is it yet another indicator of the failure of our much maligned education system?