At the beginning of The Earth, My Butt, and Other Big Round Things, Virginia Shreves is making out with Froggy Welsh the Fourth, as she does every Monday afternoon. They go to Brewster, a private school on the Upper East Side of Manhattan, and Virginia lives on the Upper West Side, where Froggy takes trombone lessons. They started flirting on their crosstown bus rides, one thing led to another, and now he's trying to get up her shirt.
It might seem like Virginia's life is pretty good, but nope, it's actually not. In fact, her best—and only—friend, Shannon, has moved across the country, the older brother she idolizes has gone off to college, and her sister up and joined the Peace Corps. But these aren't her biggest problems.
Her biggest problem is that she's fat.
Not fat fat, she tells us, just chubby fat. Still, that's enough to make her an outcast not just at school, but among her own family members, all of whom are beautiful and perfect and, well, not Virginia. In fact, she thinks she might have been switched at birth.
Virginia's daily life consists of trying to avoid the popular girls, emailing Shannon, watching lots of television, and attempting to deal with her mother, an adolescent shrink who has no time for her own adolescent daughter. Oh, and junk food binges. Lots of those.
Everything's going along as usual, which is to say it's all terrible, until the night her dad gets a phone call that rocks the family's world. Virginia's brother, Byron—the golden child of the family, and former Model Brewster Student—raped a girl after a party at which they both got drunk, so he's suspended from school and moving back home.
Virginia's life falls apart, as you might expect since she's just found out her adored older brother is a rapist, but instead of talking about it, her parents go around pretending everything's fine.
Unable to take it anymore, our heroine starts rebelling against her parents. She's determined to go out and live her own life on her own terms, and she starts by buying a plane ticket to Seattle to visit Shannon over Thanksgiving weekend. Does she tell her parents? She does not. At least, not until the last minute, when it's almost time to board the plane.
Thus begins Virginia's transformation into a feminist rebel with purple hair and an eyebrow ring. With her newfound courage, she starts a webzine, makes a new friend, starts kickboxing, and, oh yeah, goes to Columbia to meet the girl her brother raped. If nobody else in her family is going to acknowledge Annie Mills's existence, Virginia will, and she'll do it on her own if need be.
Despite having previously lived her life by the Fat Girl Code of Conduct—in other words, only make out with a boy in private, and never kid yourself that he's your boyfriend—Virginia gets herself a boyfriend at the end of the book. It's her crush Froggy Welsh the Fourth, who actually wants to kiss her in the hallway at school. She happily obliges, and if the ending isn't happily-ever-after, then it's definitely something like it.