I like it. A good marketing strategy, btw, would be to release the first one for free (the blog one), because there are many blog-in-rails tutorials and screencasts. This way people would see the alleged quality of your screencasts and be incited to buy the others.
Yes. Teaching others can definitely be a good marketing strategy. I think that Obie Fernandez made HashRocket really popular through his book, "The Rails Way"
