Symbolism, Imagery, Allegory
First, we'd like to note that the shoes in Wicked are not ruby slippers. Instead they are described like this:
From a pile of ash shavings she withdrew a shoe, and then another. Were they silver? – or blue? – or now red? – lacquered with a candy shell brilliance of polish? It was hard to tell and it didn't matter; the effect was dazzling. (220.127.116.11)
Rubies are a slightly different animal in this book. Turtle Heart probably describes their symbolism best:
"To look in glass," said Turtle Heart, pointing to the roundel he had made as a toy for Elphaba, "is to see the future, in blood and rubies." (1.8.46)
If you are interested in reading more about rubies and blood, check our discussion of "Color" below. Here, though, we're interested in those sparkly shoes.
The shoes are the one thing the Witch wants above all else, both in the movie and the book, but Elphaba wants the shoes for slightly different reasons than her movie counterpart. And no, she doesn't turn into Carrie Bradshaw.
While the movie's shoes were symbols of power, the book's shoes are symbols of love, acceptance, and family. Above all else, Nessa's shoes represent Elphaba's need to be accepted, loved, and considered important, particularly to her father.
The shoes aren't just related to themes of family and acceptance, though. They also, as in the movie, represent power. Interestingly, though, that becomes more of an excuse for Elphaba to justify her obsession with getting the shoes from Dorothy:
Should she pursue Dorothy, should she snatch those shoes away – and what were her real motives? Was it to keep them out of the hands of the Wizard ... Or was it to snatch back some small shred of Frex's attention? (5.10.1)
Ultimately, Elphaba may turn the shoes into something more than they really are.