Madeline is the protagonist. She’s intelligent, loyal, and thoughtful, and because she can only socialize with other teenagers online, her relationships with the adults in her life (Pauline, Carla, and her tutors) are especially important. She is serious and mature for her age, reflecting the fact that Pauline’s overprotection has resulted in a sheltered childhood and adolescence. She begins the story with an unquestioning loyalty to Pauline, who has been the bedrock of her family and sense of identity. As the story’s events unfold, Madeline comes to question and distance herself from Pauline’s perception of her and the dangers posed by the world outside. Madeline learns to take risks, make her own decisions, and deal with the possibility of being hurt or disappointed. She ends the book with a more adult perspective of herself, the authority figures in her life, and the world around her.

Madeline also begins Everything, Everything with a profound relationship to books, which are one of her only connections to the outside world. Yoon includes Madeline’s condensed “spoiler” reviews of the various books she reads, including Lord of the Flies by William Golding, The Stranger by Albert Camus, and The Little Prince by Antoine de Saint-Exupéry.