KoshFan
Regular
Actually, I found the last book of the series - The Final Battle - to be the most sexist of the lot. Though not the only thing that bugged me about that book, it did bug me .. especially the attitudes towards Susan in that book really gave me the impression that Lewis just couldn't handle women. Which, I found out with peaking at his biography, he really couldn't. I'm wasn't really surprised.
In the case of Susan in The Last Battle, I think it's more Lewis's dislike of teenaged women, and stuck-up people in general. You'll notice that Polly, Lucy, and Jill all have important roles in the book, especially Jill -- who's shown to have considerable intelligence, bravery, and initiative throughout.
But it's true. The man wasn't great at writing women, not only because of the times but because he knew very few of them. He was married only very late in life, I believe.