If you don't want to plough through all those essays, the key one to read is Andrew Rilstone's Lipstick on my scholar. He outlines the major issue that most of the discussion is about, which is generally known as the Problem of Susan: why is Susan excluded from Aslan's kingdom at the very end of the series? Now, he's partial, Rilstone; he more or less argues that the Problem is a straw man made up by people who want to attack either Christianity or CS Lewis himself. I think he's basically right; Philip Pullman and JK Rowling, the main (famous) proponents of the Problem of Susan theory both have a major animus against Lewis, Pullman particularly.
As far as there is an issue here, it's a "problem" with Christianity itself and its views of the afterlife; Lewis is one of the most sensitive, reasonable exponents of that view I know of. And of course, there is plenty of variation among Christian beliefs; I'm talking specifically about the subset of Christians who believe that only a few people will be "saved" through their faith in Jesus and the rest will be excluded from any reward if not actually subjected to eternal punishment. That's a view that I personally find very unpalatable, but it's not my place to criticize Christian theology. I would say that if you have a problem with that basic tenet of Christianity, blaming Lewis for it is a bit daft. Unless I suppose you think that writing a children's fantasy series as a Christian allegory was itself a morally bad thing to do, which I think some people do hold.
There's also the feminist side. I don't think either Lewis' Christianity or his writing is inherently misogynist, myself, but I'm pretty forgiving about gender stuff in novels. A book would have to be really blatantly sexist for me to have a problem with it; I don't go looking for subtext which might possibly be read as anti-women if you squint the right way. But anyway. It is the case that Susan is female, and maybe this has something to do with her fate, for what it's worth.
I'm very far from being an expert on CS Lewis; in fact, my memories of the books are extremely hazy. So I don't really have a strong view about the Problem of Susan myself, I'm just enjoying the discussion as a spectator. So here are two more essays from the previous occasion this was a big thing in the media, both intelligent analyses coming from a slightly different standpoint from Rilstone: rj_anderson being extremely erudite, and rilina's response. Oh, and there's a little bit of discussion that developed in the comments to the post where I said I was planning to make this post about Susan.
With that preamble, what I really wanted to talk about is sartorias' recent post: Lewis vs. Susan. sartorias is reading the pshat of the Narnia Chronicles, rather than the nimshal of the Christian allegory. (If English has any technical terms for analysing allegorical text, I don't know them, so I borrow the terms from Jewish Biblical scholarship.) Why, within the story's own terms as opposed to the wider Christian context, is Susan excluded? The discussion on that post is really fascinating, and covers the religious questions, the feminist issues and all kinds of different viewpoints. There's one thing that stood out for me even with all these lovely thoughtful ideas, though: this comment of papersky's.
Let me highlight this sentence from papersky's comment, because I think it really brilliantly captures the experience of feeling yourself to be the only authentic human drowning in a sea of sheeple:
When I was a teenager there was a point where it really did seem to me that my female friends were actually ceasing to be people in their pursuit of being teenagers -- it wasn't sex so much as a desire to be attractive (fashion and make-up and dieting) a desire to have a boyfriend as an accessory and a desire to be "in" (changing, or affecting to change their personal tastes in music, films and culture generally to the majority taste)The thing is, I think that's a hugely common experience among teenagers: believing you're the only one in your entire peer group who isn't totally superficial. Browsing around on LJ is a good way to get a perspective on this; you can see journal after journal after journal where teenagers, mostly girls, talk about how most of the people they know are idiots who only care about fashion and being popular, and they're the only one with ideals. I have this vision that the girls a particular unique snowflake despises are simultaneously writing in their journals about how they're so lonely being the only person who cares about anything beyond fashion and meaningless "relationships"...
I'm not going to embarrass myself by reproducing here the bad blank verse I used to write (and publish in the school magazine) when I was a teenager. I was luckier than most, because I managed to connect with other real people even before I had the maturity to realize that most people are worth getting to know, and you just have to make the effort. This led to some really intense and precious friendships; feeling that my friends and I were the last bastion of resaon against moronic popular culture was a very bonding thing. I had blue_mai, and Spanish M, and doseybat; I wasn't entirely alone.
CS Lewis was of course writing for children. If he actually intended to portray being Christian in a secular world as like being the only teenager ever to care about higher things, he was being very clever in some ways. The trouble is of course that Susan is discarded so suddenly; Lewis' readers are just as likely to identify with Susan (who is of course a very sensible and likeable person for the whole series up to the very last bit at the end) as anyone else. And the other trouble is that any really mature reader, as opposed to a child who thinks they are mature, is going to be able to see the worth even of someone who cares about mainstream culture, and therefore be annoyed that Lewis' Aslan doesn't value such a person.
While I'm (vaguely) on the subject, cakmpls has a very cool piece on The Outsider in A Christmas Carol. Scrooge, unlike the kids in Narnia, is saved precisely because he learns that he isn't actually superior to everyone else. He doesn't have to be an Outsider. Lewis' characters effectively get divine sanction for their smugness, and maybe that's the problem.