He wrote a couple of posts a year and a half ago, they still apply. In them, he explains how Amazon is making itself a monopoly, and that isn't good for anyone but them.
What's been most informative to me is how tiny publishers actually are, and how little money the author actually gets. It doesn't paint Amazon as the good guy. It's also why I buy my books hardcover now: more cash for the author.
[1] https://news.ycombinator.com/user?id=cstross
[2] http://www.antipope.org/charlie/blog-static/2012/04/understa...
[3] http://www.antipope.org/charlie/blog-static/2012/04/more-on-...