What is the theme in Ghost World by Daniel Clowes?

The book frequently employs irony to show that things are not always as they seem. For instance, the Satanist couple that Enid always sees at Angels are a very ironic couple because they defy the common expectations of what Satanists should be. The cashier at Angels tells Enid that the couple is very nice, while the common expectation of Satanists is that they are evil and mean. Furthermore, when Enid and Rebecca see the Satanists shopping at supermarket, the male Satanist has only Lunchables in his shopping cart.