In response to the previous post...

Yes, it is interesting, isn't it? Let's see if we can name them:

Magicians Nephew: Hm, they go through the door in the attic that gets them to Uncle Andrew's study, which ultimately ends up being how they get to Narnia. Does that count? When they actually get into Narnia, they go through a pool, though. :-/

The Lion, the Witch, and the Wardrobe: The Wardrobe door. (Hence, the name...)

The Horse & His Boy: Well, that didn't actually involve someone getting into Narnia from another world, or going out of it. Can't help there.

Prince Caspian: There is a door in the air that they (Telmarines & Pevensies) go through to get out of Narnia.

Voyage of the Dawn Treader: Aslan opens a door from the sky for the Pevensies & Eustace to go through. (I'm pretty sure that's how it worked, anyway)

Silver Chair: Weeeeellll, there is the door from the gardens at Experiment House that gets them to Aslan's Country, but they are actually blown to Narnia.

Last Battle: (My personal favorite book) The stable door Tirian goes through to arrive at to the Real Narnia.

So, with the exception of the Horse & His Boy, a door plays a big part in all the stories!! If there's something I've forgotten, please let me know. I'm not sure I'm thinking quite straight now...

Cheerios!