The thesis of "The Privileged Planet" is that, far from being "a small blue-green planet orbiting an unremarkable star in the outer reaches of the Milky Way" - or however Douglas Adams put it - there are various characteristics of Earth which make it exceedingly remarkable in terms of how well it is suited to complex life. No big deal, an atheist would say - that's just anthropic inevitability - if so, we may not find life elsewhere, but if Earth wasn't remarkable in that way, then we wouldn't be here to know about it.
Where they go from there, though, is to point out that the same factors that make Earth highly suited to intelligent life are also those that make it a highly suitable platform for observing the universe. Thus a clear oxygen/nitrogen atmosphere allows us to see beyond the atmosphere; it is also a good (perhaps the only) mixture for complex life. Being where we are in the galaxy allows us to see not only deep space and extra-galactic objects, it also provides a mineral-rich region in which life can exist but doesn't lead to us being bombarded by high levels of radiation from the centre of a galaxy.
As with "design" of organisms, it isn't the case that it is impossible to conceive of a better environment in which some observations could be made - but our location is probably optimum both from the point of view of survivability and observation. They also touch on cosmic fine-tuning.
Since the book is a science book, the authors don't explore any theological implications of this. What I am wondering is: ignoring for a minute whether Genesis corresponds to a historical account, what would a universe created by a (truly omniscient, omnipotent) God be like? Surely it would have to be internally coherent at just about all levels - as though it makes sense according to its own rules - like the universe we see? I have no philosophical or logical framework to hang this on, but my hunch is that an internally coherent universe (apparently working according to its own rules) that turns out to be incredibly improbable (cosmic fine-tuning) is not only required for the existence of life, and for life to be able to observe the nature of the universe in which it is, but is (ultimately) also the only way in which a god who was external to the universe and involved in creating it could signal its presence to the life without intervening directly - general revelation. Is this the ultimate significance of the "eternal power" talked about that signals the presence of God to humans in Romans 1?
I'm not sure I have expressed clearly the idea that is floating around my brain somewhere - I will try and tease it out more fully if I can sit down and think at some stage.
Incidentally, a quick plug for Wikipedia, referenced above - an open-source encyclopaedia.