A children's fantasy in the vein of C.S. Lewis' Narnia
series, or even Out of the Silent Planet, or more recently Philip Pullman. It's a little preachy at times (though not nearly so much so as Pullman), but it's hard to argue with a moral that says "Love is good, hate is bad" and "we are all individuals".
Meg can be a little annoying, but she's a pre-teen girl. 'nuff said.