Yes, they do read and check out books. Manga is very popular. And vampires.
They also want to be on the computers for what seems like forever. I am not sure exactly what they are doing, we do not monitor their games and computer activity.
They can get a little close physically - play fighting or lovey-dovey.
They can be annoying in that they can be very demanding of our attention. That could say something about their home lives and we are glad they find refuge in the library.
I just want to tell them to go out side, be active, get some sunshine. Actually, sometimes I do tell them to go outside and run around the monument ten times. And they do!
In truth, they come to the library because the staff make them feel welcome. And that is exactly what we want.
I am thrilled when a teenagers comes back years later as a grown up just to say "Hi!". We do make a difference in their lives.