It somehow seems degrading to Clowes' original comic, despite the fact that he wrote the screenplay, to whip up a big "10th anniversary" package for Ghost World that includes both the original comic and the script. The package implies that the two things are not separate but somehow complements or companions to one another and suggests that Clowes sort of has no understanding of his own work.
See, while a ton of fans of the comic like the movie and movie fans retroactively discovered the comic, the two really have very little in common. On the surface they do, but a closer look reveals a movie that's hopelessly cynical and condescending and a comic that constantly undercuts and complicates the characters' cynicism, all the while exposing their vulnerability too. Take the end of the first issue where Enid rushes home after the yard sale to see that her beloved toy still sits on the table. It brings you back to earth after a whirl of cancer jokes and lunchables-buying Satanists.
The key to understanding the core difference between the comic and the movie is to look at the sort of meta scene in which Enid goes to her local hip zine/alt. comics store to finally meet Daniel Clowes, the creator of her favorite comic. Of course, she's developed an image of him as suave and cool and with-it. When she arrives, she doesn't even approach him, seeing the slovenly, bug-eyed, balding creator from afar and being grossed-out. It's a brilliant scene for a number of reasons, all of which are worth unpacking.
First, it's Clowes' way of distancing himself from his creation. The same way the on-the-outside cynical Enid grasping her childhood toy, happy it wasn't sold, undercuts and complicates her personality, Clowes putting himself in the comic as a dopey creep, undercuts the implicit "with-it"-ness it would be easy to think he thinks he has with his female characters. Yes, he's created these characters and yes he empathizes with them, but he's still aware and feels it necessary to point out to readers that he knows he's not anything like them. And despite some emotional understanding he'd probably have for them, they just wouldn't get along.
In terms of characterization, the scene exposes Enid's adolescent idealism and ignorance. She's still young and dumb enough to think that the creator of this comic would just have to be some cool, awesome hip dude that she'll marry. It underscores the characters' lack of empathy and her like, internalization of everything around her. Ghost World's great for the way it's both highly accurate and in-tune with its characters while also not totally siding with them or holding them up as paragons of cool.
There's no scene in the Ghost World movie that references or says the same thing as the Enid Coleslaw meets Daniel Clowes scene from the comic. It would've done the movie a great deal of good to have a scene where Enid goes to meet her favorite director Terry Zwigoff only to see him as a mumbling, messy-haired old dude.
But there's something even stranger going on in the Ghost World movie and that is that the sort of Clowes/Zwigoff double of the movie ends up sleeping with Enid! Yes, the sex is weird and sad, but it ends up being used to show more the way Enid's sort of callous and fleeting--the old record nerd man is wounded by it--than any sort of overarching comment on age and implied artistic (dis)connection or whatever.
That Enid even goes so far as to have sex with anybody in the movie also shows how far the movie strays from the original comic. Nothing that big or exciting happens in the comic--until Enid bolts at the end, giving her final action of any kind added weight and meaning--and that's sort of the point. And the argument that this was movie and something has to happen would have more legitimacy if the original incarnation of the story wasn't in an art-form best known for superhumans saving the world and shit.
Before this "10th anniversary" edition of Ghost World, I held onto some strange belief that maybe Clowes wrote the movie--and Art-School Confidential--to just sort of cash-in on the hip, irony-filled "indie" culture that's increasingly pervasive (There's a long history of serious, non-film artists using Hollywood for dough). But now, the two are placed side-by-side in a book, like the companions that they simply aren't. I'd suggest going to eBay for an older edition, it'll leave a less bitter taste in your mouth post-reading.