So, you want to buy books for your library. There are a number of selection tools online that can help librarians pick the best books for their students. Check out the links below.

​ERAC (recommended in the BC curriculum) 
Canadian Review of Materials 
ABPBC
Follett Titlewave
NoveList
School Library Journal
Horn Book
Kirkus

One more thought...

The librarian may not be able to speak for all orientations, cultures, genders, and socio-economic classes, but (ideally) their diverse collection of media does. This makes them an important ally to students who are underserved or underrepresented. Libraries can provide recognition to students who are marginalized, and librarians can be conduits for this recognition.