As I summarize, please keep in mind that the author is just to present information that he thinks will help parents make decisions about what their children are reading/watching, & to reveal some misinformation currently being pushed. If, after considering everything, you're still fine with your children reading whatever, then he won't say anything about it. Also, he is writing from a Christian viewpoint, so if your viewpoint is different, you may very well disagree with him. For everything I'm summing up, he gives details, explanations, examples, etc.
Narnia & LOTR: Christian BASED books (either blatant or subtle), with strong messages about morality, good being absolute, good power coming through proper authority, evil being defeated only by good, etc. Narnia has very obvious allegories to Christ & Christianity. LOTR doesn't have an obvious religious system, but is very much a moral book. Despite being "religious" books, neither actually preaches their viewpoint.
HP: Not Christian based. Members of occult groups have praised the books as a very good way to create interest in their societies/beliefs, & have mentioned how "realistic" they are. Does not uphold absolute good, but is humanistic & relativistic instead. "Good" is good only in relation to worse evil. The only people who are really interested in upholding rules are the ones that are written so you hate them (like the Dursleys(?), Snape, the janitor (sorry, forgot his name), etc.). The children have no interest in obeying or respecting adults. Misbehavior is not only common, but is glorified & rewarded. Even the adults don't behave morally. Lying, cheating, stealing, bullying, swearing, & innuendos abound. Power is power no matter where it comes from, & both sides use the same weapons.
Children & reading: Discusses some developmental truths, including why children are more impressionable by nature & how publishers & marketers are taking advantage of that. He also lists some so-called "fantasy" writers that should be avoided by Christian children (and quite likely ALL children!). He also addresses the "I'm so glad my child is finally reading, I don't care WHAT he reads!" issue & whether or not HP has actually increased overall children's reading or not (not).
Fantasy in general, & children & fantasy: Why read fantasy at all? I love this (mangled by me) quote: "People say that children shouldn't read fantasy because it teaches them that there are dragons. But children have always known there are dragons. Fantasy teaches them dragons can be killed." He discusses the hallmarks of true fantasy (as opposed to horror, "adventure," occult, etc), one of which is HOPE, and how to find good fantasy & why to avoid the bad stuff.
Children & media: Why your children are in FOUR marketing groups & are a major target even for adult material. What to be aware of in advertising, books, movies, television, etc. Also discusses why the government CAN'T censor media (but does already have protections for children, & why that isn't censorship), but parents, libraries, schools, etc, not only CAN, but SHOULD.