...O'Brien, a devout Catholic author and professional artist, begins by reminding us of the importance of symbolism in both the Bible and literature. It was once the case that western culture was based on a Christian world-view which understood the proper use of symbols. Now, however, there has been a culture shift toward paganism, and symbols in children's literature have been perverted to reflect this shift.
Dragons are one of the symbols which is now being used in an inappropriate way (thus, the title of the book). In the Bible and in traditional literature, dragons represent evil, reminding us of the serpent in the Garden of Eden. Slaying a dragon in a story was a victorious triumph over sin. O'Brien says, "In literature of the West dragons have been regarded as powerful agents of evil, guardians of stolen treasure hoards, destroyers of the good and the weak (children, maidens, small idyllic kingdoms), and on the spiritual level, a personification of Satan prowling through the world seeking the ruin of souls."
In modern society, however, dragons are no longer portrayed this way. From "Puff the Magic Dragon" to Disney's Pete's Dragon (he discusses Disney's worldview in the book), dragons are cuddly, helpful, magical and possibly misunderstood creatures. The long-standing symbolism of dragons personifying evil has been turned upside-down, confusing the imaginations of young children in the process.
This is just one example given by O'Brien to explain the trend toward paganism today. Does he suggest that we should therefore avoid all fantasy stories? Not at all. Rather, he gives parents tools to evaluate what is appropriate and why as well as what to avoid. He even names some names although this book was written before the Harry Potter phenomenon (here is an article he later wrote about the Harry Potter stories.) There are also no sacred cows for O'Brien as he points out some ideological inconsistencies in the stories of Lewis, Tolkien and Macdonald while holding them up as generally good examples of the proper use of fantasy literature. He also has a well-reasoned defense of traditional fairy tales.