It's a hard-sci-fi story about how various societies, human and alien, attempt to assert control & hegemony across centuries of time (at times thinking of this as a distributed systems and code documentation problem!), and how critical and impactful the role of language translation can be in helping people to understand unfamiliar ways of thinking.
At the novel's core is a question very akin to that of Nagel's positivism-antipositivism debate [1]: is it possible (or optimal for your society's stability) to appreciate and emphasize with people wholly different from yourselves, without interpreting their thoughts and cultures in language and representations that are colored by your own culture?
What if, in attempting to do so, this becomes more art and politics than provable science? Is "creative" translation ethical if it establishes power relationships that would not be there otherwise? Is there any other kind?
Deepness is not just a treatise on this; it places the reader into an exercise of this. To say anything more would delve into spoilers. But lest you think it's just philosophical deepness, it's also an action-packed page-turner with memorable characters despite its huge temporal scope.
While technically it's a prequel to Vinge's A Fire Upon The Deep, it works entirely standalone, and I would argue that Deepness is best read first without knowing character details from its publication-time predecessor Fire. Note that content warnings for assault do apply.
[0] https://www.amazon.com/Deepness-Sky-Zones-Thought/dp/0812536...
[1] https://en.wikipedia.org/wiki/Logical_positivism / https://en.wikipedia.org/wiki/Antipositivism