Growth Hacker Marketing: A Primer on the Future of PR, Marketing and Advertising book by Ryan Holiday 

"A new generation of megabrands like Facebook, Dropbox, AirBnb, and Twitter haven't spent a dime on traditional marketing. No press releases, no TV commercials, no billboards. Instead they rely on a new strategy-growth hacking-to reach many more people despite modest marketing budgets. According to bestselling author Ryan Holiday, growth hackers have thrown out the old playbook and replaced it with tools that are testable, trackable, and scalable. They believe that products and businesses should be modified repeatedly until they're primed to generate explosive reactions. Holiday offers rules and examples for aspiring growth hackers, whether they work for tiny startups or Fortune 500 giants"--