The Roman Index of Forbidden Books: Now Available!
It should be said in the interest of full disclosure that this is definitely a Catholic-made and pro-Catholic treatment of the churches' old style tendency to forbid (and later merely reprove) literary works on a theological, ethical, and political basis. However, that does not render it uninteresting; the index here alone for its era of manufacture (of a large number of works the index listed at the time) is fairly good fodder for those who want to obtain material the papacy found objectionable; notably Darwin's work and a great deal of philosophical material. Oddly, this very work refutes the idea that the index provides any help to those seeking to read "anti-catholic" materials.
It goes through the elaborate process used to determine whether works shall or shall not be forbidden, and the spiritual implications of authors who accept or refuse the judgment, as well as listing the reading of such material as a potential mortal sin, as long as enough of it is absorbed.