A central theme in the book "Can You Keep a Secret?" by Sophie Kinsella is the idea of finding solace and joy in art, notably jazz music. The phrase "We'll always have jazz" suggests that no matter the circumstances in life, the timeless essence of jazz remains a comforting presence. This embodiment of resilience is mirrored in the protagonist's journey as she navigates personal dilemmas and relationships, offering her a sense of escape and connection to something greater.