1) Carrier on a campus 2) It may keep readers hanging 3) Reader holder 
A book bag is a durable bag, satchel, or backpack that is used to carry books and sometimes other supplies such as notebooks, ring binders, and file folders, particularly by students. Typical designs include backpacks, hand-carried briefcases, bags with drawstring closures that can be hand-carried or worn over one shoulder, and messenger bags that...
[n] - a bag in which students carry their books
noun a bag in which students carry their books
a bag or satchel used esp. by a student for carrying books.