Jupiter by Ben Bova
There are two main themes in Jupiter. Not too surprisingly, one is the exploration of Jupiter, with a speculative view of life and a search for intelligent life there. The other major factor shaping the story is the efforts of religious conservatives to control the government, society and even scientific work.
Grant Archer is a grad student interested in astrophysics. He'd like to spend his mandatory public service elsewhere, but the New Morality has him sent to the Jupiter research station where they demand he spy on scientists. The fundamentalists suspect there is research on Jupiter life forms that conflict with their restraints on science. Archer has conflicting motivations and concerns about doing this. There are also worries and displeasure with being post far away from his new wife for years. We follow him dealing with these issues, frustrations with work at the research station, and further character developments.
An important component of the story describes the technology used to send a research vessel far down into the crushing pressures of Jupiter's ocean. The preparations also involve using technology on the crew as well. During these explorations we get a look at a number of Jupiter life forms - some in the gaseous atmosphere and some below the threshold where it becomes liquid.
The vessel experiences a number of crises which drive much of the plot during that section of the book. This in turn has significance for questions about Jupiter life forms.
For my taste, there is too much of the book involved in political machinations, intrigue, professional competition, etc. The science part of the book plays a greater role than in, for instance, Bova's The Precipice. But as in The Precipice, the opportunities available to picture new places and explore the unknown seem short-changed by the quantity of the other material. But even if we don't have a full novel's worth of scientific speculation and the like, we do have at least a novella's worth in Jupiter.
... I'm not sure I found it convincing that life evolved to intelligence in those extreme conditions. The combination of the strength to withstand the pressure, yet still have the flexibility to move would be very difficult. I can't imagine life beginning under those conditions. But perhaps life could begin higher up in Jupiter's atmosphere and as it evolved develop creatures that could live progressively lower down. Bova does not seem concerned with how it could have come to be.