School plays work because they include every child. They include every child so every parent buys a ticket. These parents convince friends and relatives to come. Like any social event, once everyone seems to be going, everyone else goes.
That’s thinking 3 moves ahead, you can really ramp this up on the internet.
Create an eBook project, 100 community members each get a page to share their best advice. Everyone featured will be eager to promote the eBook, you can advise them how. Encourage them to post it on their Facebook profile to their 150 friends.
That’s over 15,000 people. Now be sure to add a line in the eBook such as “tell us and fellow readers over Twitter which chapter you liked best. #ebooktitle”. That’s 15,000 people who are now promoting your eBook to their 70 followers on Twitter.
You’ve just reached over 100,000 people.