Chanur Saga: The Pride of Chanur / Chanur's Venture / The Kif Strike Back Book

In my view, the first four volumes of the Chanur's Saga ("Pride" to "Homecoming") are one single big book (although one can read "The Pride of Chanur" as stand alone).
The most challenging book I have ever read.
One of the most feminist books as well. At some places it's almost outrageous!
The book is told totally by alien point of view. There is only one human mucking about, and the characters have to do some wild guesswork on his motives most of the time. As alien species is described the hani have very different (from humans) etymology, social behavior, body-language and face-expressions. Cherryh has done some master work here - one just have to admire her thoroughness. Not one human reaction slipped trough into a hani for about 1500 pages!
Astrophysics in the books on very high level, I really enjoyed it - very graphic, very detailed. Especially entertaining I found the manner of ship's behavior in close-to-speed-of-light conditions compared and related to still objects and normal velocity objects.
Seven alien species - for four of them, very fine detail description work, down to economic relations, social structure, politics, history, evolution, and genetically-driven behavior. Especially like the politics and the close relation to economic interests.
Refined character build, very good physiological motivation behind the actions of the main characters.
All in all - my favorite of Cherryh's work.