“Behind the walls of federal prisons nationwide, chaplains have been quietly carrying out a systematic purge of religious books and materials that were once available to prisoners in chapel libraries.” While titles by C.S. Lewis, for example, make the list of government-approved religious works, it is not a very long list. Some who minister to prisoners “say that an administration that put stock in religion-based approaches to social problems has effectively blocked prisoners’ access to religious and spiritual materials — all in the name of preventing terrorism.”