Though you do make a good point in your first sentence. It does depend on the goals and the audience. But I think your audience is a bit too widespread. People who have some programming experience are too wide of a net. I think if it were sold as a book for people who havea bit of web development experience then your conversion rate would be higher (from free reader to paying customer).
Now, I'm not knocking on your accomplishments. My approach is merely from the business perspective of marketing you book and videos. Have you tested other approaches? If so, may you shed some light? I used to market/sell books on the web, and find it fascinating. If you wish to continue this conversation through email mine is in my profile.