"Of Sound Mind" is a young adult novel by Jean Ferris, first published in 1990. The story is set in a small town in Vermont and follows the life of Theo, a teenage boy with a talent for music. Theo's mother suffers from a mental illness that causes her to behave erratically and unpredictably, which has a profound effect on Theo's life and relationships. When his mother's condition worsens, Theo is forced to confront his feelings of anger, frustration, and sadness, as well as his own fears and insecurities. Along the way, he discovers the healing power of music and learns to connect with others in new and meaningful ways. The novel is a sensitive and insightful portrayal of mental illness and its impact on families, as well as a celebration of the transformative power of music and the human spirit.