A quick review of this book, which was trailed briefly below.
The authors make the point that there is a very high correlation between a habitable environment and an environment which permits observation of the universe. This is the case on all scales - planetary, solar system, galaxy, cosmic era and universe. It is not an intuitively necessary connection.
This observation also runs counter to the so-called "Copernican" principle or "Principle of mediocrity" - which says there is nothing special about where we are - we "just happen" to be here. On every scale, the authors demonstrate that, were our environment slightly different, not only would we not know so much about the cosmos, but it would be a lot harder for us to survive.
They argue that the closeness of this correlation suggests that the universe is designed. If we were simply talking about a habitable environment, you could argue that this was simply necessary given that we are here. But the fact that we can also observe the rest of the universe, deduce its nature, and conclude that not only are habitable environments not the norm, but neither are environments in which we would be able to make the same observations of the universe - these facts together argue for intelligent design.
A meaty, provocative book - apparently there is a video that goes with it, available in the US from the Discovery Institute and in the UK from Penfold Books - and a tie-in website. If you liked Just Six Numbers, you should enjoy this.