This document discusses viral marketing and how it works. It begins by defining viral marketing as marketing that spreads itself from person to person like a virus. It explains that successful viral marketing campaigns leverage existing social networks by having early recipients share marketing messages with friends and family. Specifically, the document recommends creating a free e-book with valuable content that people will want to share, as this can activate viral spread with little additional cost to the marketer. The goal is to create memorable, helpful messages that people naturally want to spread among their trusted social connections.