I understand why you want an E-mail address in exchange for the book. What I don't understand is why, in addition to that E-mail address, do people have to cre

I understand why you want an E-mail address in exchange for the book. What I don't understand is why, in addition to that E-mail address, do people have to create an account of some kind? Why not just the E-mail address? The "Get the Book" page does not explain any of this, and left me puzzled as to what I was creating an account for.