The Quiet Invasion by Sarah Zettel
The Quiet Invasion has more than one good subplot or story. What impressed me most was the portrayal of a non-humanoid extraterrestrial species. The aliens are not inherently good or evil or wise or dumb. We are shown an alien society where individuals have different points of view. Some are more idealistic, some are more "practical". This species has evolved on a very different world -- so different they would consider Venus a desirable place to live. Their unique home world has shaped their culture and habitats. It struck me as a well developed picture of non-humans. Yes, there are aspects of the described society that one could find reminiscent of a known human society, but I suppose it would be extremely difficult to make a readable view of a society with no human parallels. Readers who like views of different aliens, different societies, and/or different habitats should find this interesting.
Like humans, their home world is facing a crisis threatening survival there. (Their crisis seems to be more immediate than ours.) Their search for an alternative planet has only led to finding one promising world: Venus. They are involved in the process of determining what to do.
Meanwhile, a single human community exists on Venus. As much as its leaders have worked hard to make the community a viable and desirable start to colonizing Venus, the task is long and expensive. The funding is drawing to an end and the community is faced with whether it is able to continue.
Then some scientists in the human Venus community report evidence of extraterrestrial artifacts. Interest on Earth about Venus increases and funding possibilities open. But political issues arise. And scientific investigations of the evidence of aliens raise doubts.
We get a view of a struggling human colony on an inhospitable world, scientific investigation, efforts to communicate and negotiate with aliens, etc. There are ethical issues and interplanetary jurisdictional questions for both humans and aliens. It is a thought-provoking book.