This looks to me like a pretty in-depth newsletter on how best to use Outlook.
I don’t think it gets into the design of the software, but it seems to get into some useful distinctions about how best to manage tasks.
Once again, however, the system described happens to match the one that the author uses, rather than clearly describing a range of options for all users. It might be because the ideas behind the system are all contained within the book, rather than shared in a blog, and the site is one of those developed by the publisher in order to sell more books.
While the approach is very old-school, the thinking seems to get a bit deeper than usual.
The system is called “Total Workday Control” and the ideas I read were described in the author’s newsletter.