Books inherently possess the gift of knowledge. Unfortunately, just as Adam and Eve ate the forbidden fruit from the Tree of Knowledge, the information shared by certain books could also entice man to sin. The Church is concerned and protects her people from such undue temptations. It is a fact that there are some books that reveal very convincing arguments capable of misleading the faithful in the course of their spiritual journey.
Take, for example, the very shrewd novel entitled The Da Vinci Code, written by Dan Brown, which undoubtedly incited clamor in the world. Another excellent example is the Satanic Bible itself, which obviously contradicts the teachings of the Church but is beautifully and logically written, with tenable arguments that could easily sway the philosophy of its readers.
The act of the Church forbidding certain books to be read by the people is done for the sake of the common good. When you pray the Our Father, you ask God to “lead us not into temptation”; the books forbidden by the Church are actually temptations that are highly capable of leading God’s children to sin. They tempt you by offering information (many times they do so by using strange controversies) which will strike your curiosity and even share with you various facts on a subject. Unfortunately, said facts are also mixed with lies and some deceitful claims done in a shrewd and subtle way.
This does not, in any way, imply that the Church has no confidence in the people. On the contrary, it shows how responsibly the Church responds in particular situations which threaten potential risk at the expense of the faithful. The Church also serves as the spiritual counsel of the people that aids in their spiritual development; hence, for the Holy Church to waive her goodwill and allow the proliferated readings of articles or books which the Church recognizes to contain illicit and deceitful contents would impede the growth of holiness of the faithful.
The Church does not hide information from her people. After all, you can still purchase those “forbidden” books from a bookstore. But the Church is already aware of the unhealthy contents of those books. She knows that said books have the capability to ruin a person’s spiritual growth by preaching information (usually a crafty mixture of facts and lies) adverse to the teachings of the Holy Church. The Church warns that the readers will draw fraud, very convincing lies, and other misconceptions, and they might recognize them all as facts. Unfortunately, when that happens, the Church will not be on the ground of advantage to defend and explain the truth of the matter to the faithful.
The Church is universal and seeks to advance the common good. She has the noble intention to promote the advancement of spiritual growth and to protect the faithful from undue influence which could lead them to sin.