I would recommend
Hey, Whipple, Squeeze This: The Classic Guide to Creating Great Ads
It's a great book for every entrepreneur who starts to promote their products/services. The voice is so friendly and the examples are also very practical as well. I took some advice from this book to set up social media channels for my product - Petgotchi!
Agree Josh. It was a trendsetter for lean startup movement. Other good books in the series include Lean Product Playbook by Dan Olsen and Ash Maurya's book
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