Out of curiosity: Why do you write a book and let it be read publicly if you sell it as well? Why should somebody buy a book when all the content is available f

Out of curiosity: Why do you write a book and let it be read publicly if you sell it as well? Why should somebody buy a book when all the content is available for free? Is this done to create some awareness for the book and thus to improve SEO (e.g. generating good backlinks, etc.). And later you restrict the public available content once SEO backlink power is generated? Our of curiosity 2: Are you happy with the sales, how many books could you sell already (if you don't mind to tell us)? Would you write again a book about a console-based app? Out of curiosity 3: Are you happy with Leanpub? Thanks!