Publisher’s Weekly has the results from Understanding the Children’s Book Consumer in the Digital Age, an ongoing study from Bowker Market Research.  The trends seems to be affected by the recent blockbuster films and series like The Hunger Games, but also goes well beyond those:

“Although bestsellers lead, there’s a long tail of rich reading that has interesting implications for the publishers of YA books in terms of discovery and consumer relationships,” said project editor Kristen McLean.

Adult readers of teen books appear to also have the most valuable of traits to publishers.  They are early adopters of e-books but willing to purchase a book they want in either print or digital format.  They are loyal to the authors they love and they are active on social networks and get reading recommendations from their friends.

Sounds like a lot of the folks I know online and in person who read these books.

UPDATE:  Thanks to a tweet from @ScottWesterfeld, I realized that I misunderstood the study results.  55% of BUYERS of YA books are adults while 28% of sales are to adults.  Of those, 22% are reading the books themselves.  My apologies!