More and more GNs are being published for all age groups.
Make sure that what you order for your library is suitable.
If your library is part of a K-8 school or 6-12 School consider dividing your GN section into age appropriate collections as you might your fiction and nonfiction.
Keep in mind, that at times publishers rate a series, before they know how it will turn out. So the first few volumes in a series might start out appropriate for your collection and later might turn too mature.