I have always been a fan of hard science fiction, and Diaspora fits the bill. There is a very light setting, with no faster-than-light travel, although there are slip-points connecting the various system in a cluster.
A big part of the game allows the players to define their own cluster, giving a nicely built structure to do so, allowing them to define the setting for the game.
The system itself is fairly standard FATE, as found in Spirit of the Century and Dresden Files, with some minor variations. The characters are designed to be created cooperatively, and the character design process ensures that they are all well-connected to each other.
There are four detailed combat systems (or mini-games, since each one is actually playable as a wargame on its own). They include personal, platoon, starship and social combat.
The first three are fairly standard, and well executed. I was really surprised by the quality of the social combat chapter, and I honestly feel it is the best implementation of social combat that I have seen in any system, since it uses zones not to model the physical space, but rather levels of intimacy and points of view. Even if you use nothing else in the book, the social combat is worth the price of admission.
The book is then rounded out with an equipment generation chapter, allowing the players to create the various technologies to round out the setting.
Overall, Diaspora is a brilliant game, and perfect for lovers of science fiction and FATE. Diaspora is an excellent hard-science space opera game.
The Kindle edition itself suffers from some problems, and the tables in the book are a bit hard to read on a Kindle, so I would recommend getting the PDF version if you really want the game.