This classic book by Robert Cialdini will help you sell more online as it contains six principles of persuasion which make people more likely to click on things. Although the book does not specifically deal with the Internet, the ideas contained within this book can be applied in a variety of circumstances. The chapter on Social Proof,  however, shows just why social media has become so important in helping online businesses to grow. Similarly, you’ll discover in the chapter on Reciprocation, why those pop-ups asking for your email address actually do work. This book is full of examples and case studies that you can learn from. If you want to increase your chances of success – either from your website, or face-to-face, there is a great deal you can learn from this book.
Influence: The Psychology of Persuasion