5 Stars without a doubt. The amount of content you can find within the pages of this book is simply amazing. GM tools for creating your space sandbox (and running it), elegant but simple rules for important scifi tropes/scenarios (mechs, AI, starships, tech equipment, cyberware, drugs, hacking, etc.) and finally a simple method of character creation with lots of options and opportunities for diversification. This is the working mans' space RPG, with a system simple enough not requiring you to spend hours on preparation yet with enough customizability that not every character/situation at the table feels the same after a few gaming sessions.
SWN is not a product without its problems though, don't get me wrong. While the authors creativity is unparalleled (at least from my point of view) and they clearly know how to write functional and elegant rules for their game, the presentation of those rules ist somewhat unoptimized. Often one sentence clearly states a rule, while the following paragraph seeks to explain this rule (hint: not needed!) and instead brings up new questions or contradicts the statements made one paragraph earlier. This is but a minor issue, since most rpg books are plagued by these problems, and thus doesn't modify the 5 star rating.