I avoid most YA books because they seem to be targeted at someone else. I don't a different age, because I can read books that are targeted at a younger audience, I mean so much of the young adult category seems more targeted at young adult girls rather then young adult boys. Nearly all the titles I see seem to be trying to ride the Twilight wave.
When I take my son, who is a young adult himself at 12 years old to the book store, we look at the young adult section but he looks at all the new books there, reads the cover jacket / back cover blurb, sometimes flips through a few pages to see what it is like, and puts it back saying "this is a girls book". Sure you have some titles like the stuff from Michael Scott about Nicholas Flamel or the Percy Jackson books, but going to a lot of book stores with a kid and seeing the YA section a lot, those are in the minority.
Young Adult at some point became Young Adult Female. So neither I nor my son are the audience for the category in general.
But maybe that is just my impression and things aren't quite like that.