This is an interesting and useful book, just not what I expected. I thought it was full of advanced techniques for detecting obscure, subtle and difficult symbols in literature. No, it's mostly about recognizing themes and what those themes often mean: specifically how literature draws on older literature and on myth, repeating and reconsidering common themes.
In the chapter about Christ-figures in literature, the author's tone suggests that he's probably approaching the subject from a Christian worldview.