Revelation Space, the series as a whole, is amazing.
Anyway I think I would like to make a few contributions myself.
The Foundation Series by Issac Asimov. While most certainly not in line with the overall Starsector theme I think it has several points of familiarity. Collapse of an empire most prevalent, obviously. Also just a damn classic. Certainly more about humanity and society than laser pewpew.
The Expanse by James S.A. Corey. While a lot of other stories deal with an already galaxy spanning empire, which is fun, The Expanse brings it all to before man has even left the solar system. Not even Mars is fully terraformed. However, it already illuminates just how much of a powder keg human civilization is. Also, at least the first book Leviathan Wakes, has a very nice noir theme as well. Also more mystery than blowing things up. Though that does happen.
Red Rising by Piece Brown. Again not totally in line with Starsector. Just as with The Expanse the story takes place in the solar system. No galaxy spanning empire here! However, there is a heavy influence from Roman myths, which is always a plus right? I mention this because of the empire the Golds have created and the collapse that they strive to keep at bay. A lot of blood generally.
Would also suggest Jack McDevitt's A Talent for War.