Anyhow, first book: Michael Ward's Planet Narnia. The author argues that each of the Chronicles represents one of the seven medieval heavens and the Roman god who presides over the attendant planet of each. The Lion, the Witch, and the Wardrobe, for example, follows the Jovian of the renewal of life after a period of death and the restoration of just rule couched in divine righteousness; Dawn Treader abounds in solar imagery and concerns an Apollonian quest for the sake of pure knowledge, etc.
It's an intriguing premise, and I do think Ward's onto something, but his argument's weak in many spots, and, man, does he make it oddly. The book seemingly was never rewritten from its origins as a doctoral thesis, and there's a lot of "I need to hit page count" bloviation and pointlessly-ornamented language. Ward has some really bizarre hang-ups that needed editorial trimming (science embraced the theory of evolution as a way of proving medieval alchemy? really?), and he makes his book as much about C. S. Lewis's obscure Ransom sci-fi trilogy as it is about Narnia. The argument itself has problems: the book-to-planet correlations for Luna, Mercury, and Venus are pretty weak, and even the strong chapters contain a lot of apophenic reaching - hey, Jupiter's traditional color was red, and Jadis has red lips, and Mablung has a red maw - and look, there's a Great Red Spot on Jupiter! Ward got a documentary made on his ideas (The Narnia Code, unseen by me), and though I hope he refined his argument for it, I'm not hopeful.