First I developed a list of topics that applies to each of those three stages: Introduction, History, Castling, Theory, and Notes. Then I went through the early chess960 posts on my main blog -- up to the point where this current blog took over -- to see if they fit into the 1-2-3 structure. Finally I created a new page, Chess960 1-2-3, which incorporates all of the above.
A single index page is a long way from an ebook, but it should evolve over time. Because it's a static page, a link will appear at the top of every post on this blog.