Evil Is Sexy: Both Digory and Uncle Andrew are impressed with Jadis' beauty; Polly on the other hand is quite immune.
Fanfic Fuel: The Wood between the Worlds. There are countless, possibly infinite portals to other worlds, but we only see three: Earth, Charn, and Narnia. This book also reveals that, in Earth's ancient history, Atlantis was real and Fairies existed, neither of which is ever mentioned in any of the other books.
Fandom Berserk Button: Don't call this the first Narnia book. While the earliest in the series' chronology, it was written second-to-last and the multitudes of Call Forwards are lost on anyone who starts with it. And it really doesn't help that some editions label it as number one.