Dear Student,
Certain books were prohibited or banned during 15th and 16th century by the church. These books were listed under, "Index of Forbidden Books". The purpose of this act was to prevent the contamination of the faith or the corruption of the morals of Roman Catholics. The Church believed that through the reading of theologically erroneous or immoral books, people's mind gets corrupted. It is also considered that the Church did all this to retain its powers and rule the people.
Regards,