Don Tillman, though never explicitly labeled, exhibits traits of Autism Spectrum Disorder. He thrives on routine, struggles with social cues, and approaches life with a unique logic-driven perspective. Simsion masterfully portrays Don's experience, not as a deficit, but as a different way of perceiving and interacting with the world. Through Don's journey, the novel encourages us to embrace neurodiversity and recognize the unique strengths and perspectives individuals on the spectrum offer.

Don begins his quest for love with "The Wife Project," a meticulously designed questionnaire aimed at finding a perfect match. However, he soon meets Rosie Jarman, a free-spirited woman who throws his carefully constructed world into disarray. Rosie is everything his questionnaire deemed incompatible, yet he finds himself inexplicably drawn to her. This highlights a central theme: love defies logic and often arrives in the most unexpected ways, challenging our preconceived notions and pushing us outside our comfort zones.

Don, through his interactions with Rosie and the challenges they face, learns to appreciate the beauty of imperfection. He begins to understand that life's greatest rewards often lie outside the realm of rigid planning and control. As Don embraces spontaneity and learns to adapt to unpredictable situations, he discovers a newfound sense of freedom and joy, ultimately leading him to a deeper understanding of himself and the world around him.