Nikki is a fourteen-year-old girl entering her first month at the elite Westchester Country Day Middle School on a scholarship. Lacking the designer clothes and cell phone she believes are required for popularity, she writes intensely emotional entries in her diary about her desperate desire to fit in with the wealthy crowd. She harbors a secret passion for art that frequently clashes with her attempts to project a cool exterior.

MacKenzie is the wealthiest, most popular eighth-grade girl at Westchester Country Day. She wears expensive designer clothing and openly mocks anyone who does not meet her strict aesthetic and financial standards. Behind her confident facade, she aggressively guards her status and hides any mundane problems that might compromise her flawless public image.

Brandon is an observant student who subverts the typical middle school hierarchy by ignoring popularity contests. He serves as a photographer for the school newspaper and possesses an offbeat sense of humor. Unlike the popular crowd, he notices people for their actual talents and consistently offers kindness to targets of bullying.

Chloe is a Latina student who bonds with Nikki over their shared status as library shelving assistants. She enthusiastically pursues a trip to National Library Week in New York, organizing ambitious projects like book drives to prove her dedication. She often makes impulsive decisions about group activities.

Zoey is an African-American student who immediately welcomes Nikki into her existing friendship with Chloe. She shares Chloe's obsession with earning a spot on the New York library trip and possesses a strong rebellious streak when denied what she wants. She handles the logistical scheduling when the group launches a book donation project.

Nikki's dad is a professional exterminator whose contract with the elite middle school provides the scholarship for his daughter. He drives a highly visible work van topped with a giant plastic roach. He remains completely oblivious to the deep social embarrassment his job causes his teenage daughter.

Nikki's mom is a practical parent who attempts to guide her daughter through the transition to a new school. She values journaling over expensive electronics and easily falls for her daughter's attempts to fake illnesses.

Nikki's little sister is a highly impressionable young girl who absorbs everything her older sister tells her as absolute truth. She develops an intense, prolonged phobia of the Tooth Fairy that dictates her behavior and reactions to strangers.

Nikki's grandma is an active senior citizen who fills her days with hip-hop classes and daytime television. She offers blunt, sports-metaphor advice when her granddaughter calls in distress about school drama.

The school librarian is a faculty member at Westchester Country Day who oversees the student shelving assistants. She holds the power to select three students for an exclusive spring trip, inadvertently sparking a massive tattoo-for-books economy in her library.

The hearing-impaired neighbor is an elderly woman living near Nikki's family who loses her hearing aid in the grass. She frequently misinterprets conversations due to her hearing loss, resulting in bizarre and disconnected verbal exchanges with the neighborhood kids.