The Discovery of Flight is a novel in two voices about the relationship between two sisters, the older of whom is disabled by cerebral palsy and only able to communicate with assistive technology (she can control her computer by moving her eyes). It interweaves the fantasy novel sixteen-year-old Libby is writing for Sophie's thirteenth birthday, and Sophie's diary, in which she discusses the deteriorating condition of her older sister. The book's title is also the title of Libby's novel, in which Libby takes the form of a hawk telepathically linked to a girl who, like her sister, is a good artist. Sophie's diary is in fact illustrated with the occasional black-and-white drawing. The sicker Libby gets, the more she retreats into her novel and the less she interacts with the outside world. Though the situation is tragic, Sophie's voice is extremely funny and wry. In addition, through her storytelling, Libby becomes a heroic figure rather than a helpless victim. After Libby's death, the girls' mother presents Sophie with the novel and Sophie writes its final chapter, bringing the voices of the two girls together.