To Pete_: Here is an excerpt from the now-outdated Catholic Encyclopedia:
Since the prohibition of books concerns all, anyone wishing to use forbidden books is bound to get a dispensation either from the Apostolic See or from some person specially authorized by the pope (paragraph 23). By paragraph 24 full powers to that effect are given to the Roman Congregation of the Index as well as to that of the Holy Office; also to the Congregation for the Propagation of the Faith with regard to the countries under it and to the Magister Sacri Palatii Apostolici with reference to Rome. Bishops as well as prelates with apostolic jurisdiction have the aforesaid power, according to paragraph 25, by virtue of their office, only in urgent cases for individual books; they are however, invested with full power, either directly by the Apostolic See or through the Congregation of the Index or the Propaganda. Dispensations are to be granted with prudence, and on just and reasonable grounds. The general authority given to bishops directly by the pope, in the so-called quinquennial faculties, may be delegated by them to others since the Decree of 14 December, 1898 (Acta S. Sedis, XXXI, 384). The bishops of England have this power from the Congregation of the Propaganda, and they make use of it by delegating it to their priests; thus, the latter may, without further formalities, give permission (e.g., to their penitents) to read forbidden books. Still a confessor, or even a bishop, who foresees that the reading of prohibited writings would expose the petitioner to great risk regarding faith or morals, would not be free to grant the desired dispensation; and if the petitioner nevertheless obtains it, he is not allowed to make use of it, since he is at all times bound by the natural law.
To repeat, however, there is no longer any such prohibition and no such dispensation is required.
If you have further scruples, you should talk the matter over with your pastor or a Catholic educator.