I saw the movie because of an interview of Daniel Clowes I heard on NPR. Then I bought the book because the movie was so good, and everyone knows the book is always better than the movie, right? Actually they're both good. Movies and comix (of the self-contained, non-superhero type) are similar enough that one translates pretty well into the other. The scene with the bus at the end, for example, is about as poigniant in the book as in the movie, but in a novel it'd just be stupid.
The art is interesting, blending a surrealistic attention to kitschy detail with a well-proportioned reasonableness. Everything is bathed in an eerie blue glow, which Clowes (NPR interview) likened to the illumination of a television screen at night. It does not shy from the boring ugliness of ordinary life.
The story is about Enid and Rebecca wresting with an adult world that, in the summer after their high school graduation, expects them to join it. As their caustic banter shows, they are very aware of adulthood's boring ugliness, and band together to resist. They rebel against tedium, with mixed success, before realizing that they need to get on with their lives. "Ghost World" tells this universal story of American life with grace and wit. I really recommend this book.