C.J. Cherryh's Alliance/Union series. Space opera, politics. Can mostly be read in any order, two exceptions; my suggested reading order follows.
Heavy Time/Hellburner (these two are a pair, direct sequels/same cast)
Cyteen/Regenesis (another pair, but feel free to read something else in between them)
40,000 In Gehenna
Also recommended: R.M. Meluch, Tour of the Merrimack (available as a two-volume omnibus of four books, or probably as the books themselves if you're buying used). Reading order: The Myriad, Wolf Star, The Sagittarius Command, Strength and Honor. Full disclosure: I've only finished the Myriad so far, but it was strong enough that I'll recommend the entire series. Military science fiction.
Lilith Saintcrow, Dante Valentine series: Working For The Devil, Dead Man Rising, The Devil's Right Hand, Saint City Sinners, To Hell And Back. Urban fantasy plus cyberpunk equals awesome.
David Weber, Safehold series: Off Armageddon Reef, By Schism Rent Asunder, By Heresies Distressed, A Mighty Fortress, How Firm A Foundation, Midst Toil And Tribulation, Like A Mighty Army. Humanity reached the stars, met aliens, they tried to exterminate us and nearly succeeded. The last outpost of humans was indoctrinated with a religion that banned technological innovation, in an attempt to keep hiding from the genocidal aliens forever. Some of the leaders thought this was a crappy plan, and had a plan B; this is what happens when that plan goes into effect.