Seems like a great concept for a book, however, perhaps just a little bit more detail on the landing page? I definitely know that this is the route you should be taking (per Nathan Barry, if you haven't read Authority, check it out), but I'd like to see just a little more detail.

What are you showing, exactly? All I see is a sign up page for a book which may or may not be finished soon.

It would be far better if there were a table of contents on this page.