C.J. Cherryh's Hugo Award-winning _Downbelow Station_ is $1.99 at Amazon (and possibly other places):
https://www.amazon.com/Downbelow-Sta.../dp/B00HFXK6KE
The central story of her Alliance--Union universe, it was written so as to provide a backstory for _Merchanter's Luck_ which serves as an excellent entrée to that series.