The author, Kevin Davey, was struggling with his business, KJ Trading Systems, which teaches advanced stock trading techniques. He had a decent-sized email list but wasn't growing it and not seeing much revenue from it. To turn things around, he analyzed various metrics such as subscriber value, acquisition costs, open rates, click rates, and unsubscribe rates to understand what was working and what wasn't in his emails. He made changes such as offering more value through freebies, establishing himself as an authority in his field, and surprising subscribers with extra rewards. By focusing on small adjustments and tailoring his strategy to his audience, Kevin was able to double his email subscriber list and significantly improve revenue without increasing advertising spend.