This is a slightly odd book.
Hal Clement has been renowned for writing SF with real science, and his early novel "Mission of Gravity" is a classic of physics and chemistry. If you can appreciate this ultra-scientific approach, with little emotional content, you might really enjoy "Still River".
The plot is fairly straightforward: five students from an advanced interstellar culture are left alone on the small planet Enigma 88 as a practical assignment towards getting their advanced degrees.
Enigma 88 is a weird place. It orbits an O-type supergiant, and stars like that aren't supposed to have planets at all. It also has an atmosphere, despite being small. Although the students are pretty capable, it doesn't take long for some of them to be in physical danger.
I said that there was little emotional content. That's because most of the species of this interstellar culture are extremely reserved by our standards and have strong codes of privacy. There is one human on the expedition, Molly, and we do learn a little more about her feelings. Perhaps deliberately, Clement doesn't give many details about this culture - it adds to the slightly odd, detached, understated tone of the book.
The author succeeds in what he surely set out to do - create a scientific SF adventure puzzle. His aliens have a definite reality about them, perhaps because they do seem to think differently to us.
If you've read anything by Hal Clement, please try this - its my favourite of his novels.