Kyle is an eighth-grade student in Alexandriaville, Ohio, known for his love of video games, board games, and puzzles. Despite not being a strong reader, he is the clever, natural leader of the hometown team that previously won a major competition. As the new Library Olympics approach, he struggles with self-doubt and the pressure of maintaining his reputation as a champion.

Luigi Lemoncello is an eccentric billionaire who made his fortune selling innovative games and puzzles. He uses his wealth to create a wondrous, technologically advanced library in his hometown of Alexandriaville. Deeply committed to making learning entertaining, he organizes the Library Olympics to celebrate knowledge while fending off critics who disapprove of his unconventional methods.

Charles is a wealthy and privileged middle-schooler from Alexandriaville. After being caught cheating and disqualified from Mr. Lemoncello's original contest, he harbors a deep grudge against the winning team and the library itself. He uses advanced vocabulary to sound important and manipulates his influential mother to try and shut the library down.

Akimi is an eighth grader in Alexandriaville and a core member of Kyle's puzzle-solving team. She possesses a highly logical mind and excels at scientific and engineering tasks. She acts as a fierce competitor who is not afraid to call out her friends when they lose focus or behave selfishly.

Miguel is the president of his school's Library Aid Society and a dedicated teammate to Kyle. He holds a deep understanding of the Dewey decimal system and general library organization. He acts as the moral compass of the group, consistently reminding his friends that teamwork and integrity matter more than winning.

Sierra is an avid reader and a vital member of the hometown Alexandriaville team. Her vast knowledge of books, history, and literature frequently gives her team an edge in trivia and research challenges. She believes in fair play and advocates for a level playing field among all competitors.

Susana is Charles's mother and the founder of the League of Concerned Library Lovers. She is a wealthy, status-obsessed woman who frequently namedrops her connection to the head librarian of the Library of Congress. She strongly disapproves of Mr. Lemoncello's technology-focused library and lobbies aggressively to shut it down or seize control of it.

Andrew is a knowledgeable eighth grader who previously participated in Mr. Lemoncello's games but was disqualified for cheating. He now claims to hate libraries and works part-time sweeping up and filling bird feeders at a motel. Despite his outward cynicism, he retains a strong grasp of logical thinking and library organization.

Dr. Zinchenko is the world-famous head librarian of the Lemoncello Library. She manages the extensive logistics of the facility and handles the practical execution of the Library Olympics. She maintains a professional, self-assured authority while easily commanding the attention of excitable contestants.

Marjory is the formidable middle-school champion of the Midwest team from Michigan. She is a highly serious, traditional student who memorized the Dewey decimal system before preschool and disdains the silly, game-focused atmosphere of the Lemoncello Library. She is fiercely competitive and confident in her superiority over the other contestants.

Woodrow, known as Woody, is the eccentric owner of the motel hosting the Library Olympics contestants. He is introduced as a distant relative of Andrew Peckleman. He obsesses over the birds at his motel, holds a passionate hatred for squirrels, and quietly approaches various contestants with suspicious offers during the competition.

Haley is a former member of the winning puzzle-solving team who starred in Mr. Lemoncello's commercials. She announces early on that her family is moving to Hollywood to pursue acting opportunities, leaving Kyle's team with only four members for the upcoming Library Olympics.

Lonni Gause is the holographic representation of the last librarian at the former Alexandriaville Public Library. Her projection frequently appears to warn the contestants and Mr. Lemoncello about the dangers of censorship, often recalling the events that led to her original library being bulldozed.

Angus is a member of the Southwest team competing in the Library Olympics. He is an experienced flyer who has been taking piloting lessons from his father since the age of six, making him a formidable opponent during the pterodactyl-flying challenge.

Abia is a contestant in the Library Olympics who proves to be highly skilled at the motion-sensor video game. She serves as one of Kyle's primary challengers during the pterodactyl flight event.