Implications: Effective marketing focuses on a consumer with the motive, the means and the opportunity to commit a purchase. In this case, the motive might be boredom during a train ride, and because most folks on a train are commuting we can assume they have the means (money) to spend on a book. And opportunity is facilitated by the use of QR codes, which most smart phones are capable of reading with the download of a simple app.
Think about your product or service. What would be the best possible timing for you to deliver your message or invitation to a consumer? Are you doing it?