The Compound Effect is a self-improvement instructional book written by Darren Hardy. The book portrays the idea that success is the result of small, continuous, impactful actions over the long term. Hardy advocates small, gradual change in our habits and behaviors to achieve big results over the long haul. It also provides practical strategies and advice for developing successful habits and overcoming difficulties. The overall message of the book is that success can be achieved through hard work, discipline, and persistence.