Interesting. But there are so many (marketing) things wrong here, I don't know where to start. For starters...<p>1) The Offer - Free might have been the wrong approach. If there's an audience that's familiar with "you get what you pay for" it's engineers. That is, free is a signal of perceived value. Pricing it at (e.g.) $15 and offering (e.g.) three free chapters could have fared better.<p>2) The Offer: Part 2 - Price and size of free sample should have been tested. Perhaps $25 and four free chapters would have done better? Or $20 and two free chapters.<p>3) Testing - It sounds like he went all in on all the distribution channels immediately. Instead, pick one or two and *again* test some ideas and offers and don't scale until you have some confidence in the banner, text, verbiage, offer, etc. whatever.<p>3.5) For that matter he should have done some testing of what he picked. For all we know, X (fka Twitter) might have been better. He assumed that what he reads is best for sales. It might reach the target but that doesn't mean anything. *No one* is smarter than The Market. And the only way to understand The Market is to test.<p>4) (Lack of) Repetition - I didn'n't see an exact number of weeks - maybe I missed it? - but getting someone's attention to the point that they act takes time. It takes that person seeing the ad over and over and over.<p>5) (The Wrong) Assumption - The smartest theory to start with is "No one cares. No one cares about this product the way we do. We have to make them care."<p>Put another way, your baby isn't just ugly, it's invisible. Deal with it.<p>Etc. Etc. Etc.<p>---<p>Interesting stuff, but in many ways this is a text book case that could have been titled: Marketing & Sales - How Those Who Write Code Get It All Wrong.<p>With that title / scope he could write a second book and sell more than the first one.