If everyone visits a factory and takes a sample, it goes out of business.

But if everyone in the community takes an idea, that idea goes up in value.

The best marketing advice I have for someone writing a book is simple: Write a book that people want to share with others. And then make it easy for them to do so.

That’s such a simple concept, and yet it’s overlooked in one media sector after another.

If you want to build a vibrant non-profit, create one where your donors do the fundraising.

If you want a hit TV show, write one that your viewers want to talk about with friends.

And if you want your software to be effective, embrace the network effect so that it works better for all users when your users bring in new users.

The five-pack is one way I’ve discovered to amplify this horizontal spread. My new book comes in a discounted set of five, with 25 free limited-edition booklets included. Each generous leader ends up with 4 extra books and 25 booklets to give away.

Of course, not everyone will choose to share an idea. But some people thrive on being nodes in the network, improving the systems that are in close proximity. When they have an efficient, leveraged tool to spread an idea, they’re more likely to do so.

People don’t share a concept because it helps the creator of the idea. They do it because it helps them. When they’re surrounded by people listening to the same music, talking about the same issues or doing work in a complementary way, things get better.