I remember being terribly disappointed with this final installment of the trilogy. It was partly the change of tone, but mostly that Lewis' always present christian sermonising began to outweigh the story. I believe that he and Tolkien would argue about the presence of christian themes in their writing - both were devout men, but while Tolkien thought the story should take precedence but still have a moral centre Lewis argued that the work should always serve to be a christian message. Perhaps it is simply this fact that makes Tolkien the better storyteller.