Books are routinely banned in prisons throughout the country for reasons that can often seem arbitrary. Most books that reach prisons do so via donations, either to prison libraries or to individual prisoners directly. For most medium and high-security prisons, books cannot even be donated by individuals or groups; they must either be purchased or donated directly by the publisher. But even in prisons where books can be donated more easily, before they hit the shelves, prisons have wide latitude to determine whether they can be allowed inside their walls.