For a mix of political intrigue with elements of "who dun it", against a background of social change and unrest with the early stirrings of war, plus brilliant characters and human expansion throughout the solar system and beyond into deep space, I
highly highly highly recommend "Heavy Time" by C.J. Cherryh, and the sequel "Hellburner" (which has added overtones of "gamers on the bleeding edge", to borrow from the "book in 5 words" thread
Hellburner is my stand-out, all-time favourite book - I've lost track of how many times I've read it).
The description on her website reads:
"Initial book of the Alliance-Union Universe, followed by Hellburner. Actually best to read Downbelow Station first, though it comes later. These are the books of the Company Wars, the foundation piece for the whole Alliance-Union Universe."
(Note: I didn't read "Downbelow Station" before reading these two books, and didn't feel I was missing anything.)
Both of these are available ($5 each) in a
wide range of DRM-free ebook formats on the website she shares with two other authors -
Closed Circle.
Only downside is that, because of issues with publishers and a desire to do the ebook thing herself (with the other two authors in Closed Circle) rather than having publishers handle it all, getting her other books out as ebooks is proving kind of slow, so might have to wait a bit before more of her Alliance/Union universe books become available. But I reckon Heavy Time/Hellburner stand on their own very well.