I think that the use of the first person narrative voice was brilliant, even necessary for this novel to have the proper effect. We are able to hear Norman tell the story from his point of view and in his own words and roll our eyes wondering if this pig-headed snob is EVER going to open his eyes to what is happening around him. Ultimately, just as he would accuse primitive societies of being trapped by their ignorance, he is likewise trapped by his own self-imposed rigid mindset. In his world view, men are cognitively and emotionally superior to women and all "reality" is merely a reflection of science and mathematics. Anything not "scientific" or at least scientific in is definition, is not reality. It is amusing and sometimes horrifying to watch him rationalize the supernatural events occurring around him.
Finally, with his wife's help (who actually would have been MUCH better off without his meddling in the first place) he is able to right what was wrong and get everything back the way it was before he intervened. You can't help but smirk when you read how he slants the action so that it always looks like he is the hero that saves the day. The real brilliance of the novel is that Norman's narration is transparent. Even while he tells you about his application of scientific principles and logical solutions to the horror confronting them, you can see the terrified Norman cowering behind it all. This Norman knows that he has left himself and Tansy naked to an evil onslaught and that he is completely out of his depth. He retreats into depression and alcohol and lashes out in frustration at those around him. It is pathetic to watch him, even though he believes in the reality of the magic, attempt to sell himself on the idea that everything that is going on is explainable by scientific, psychological, or medical causes.
Well, good triumphs over evil and at the end Tansy asks him if he has changed his mindset or if he is already rationalizing the whole chain of events into a scientific explanation. We don't get the answer, but clearly we hope that Norman has learned a bit from his wife, who has shown a tremendous amount of patience with her stubborn and close-minded husband.