I wonder if this project started off as an attempt at a straight fictional biography, like Doctor Mirabilis which is also about a scientist who falls foul of the Catholic Church? Hard to say, but it stands as a science fiction story in which Galileo is contacted by humans from the distant future who want him to help with a problem they are having on Europa...
So there are two stories, one about Galileo's life from the start of his work on telescopes up to his death and another about dreams of Europa where strange and complicated things are happening and something has been discovered in the ocean...Eventually these two threads intertwine and start to affect each other in dramatic ways.
This book really ought to be a failure. Chunks of it are theme and variation on Galileo is debauched, ill, irritable and always short of money - it should get boring but it never quite does. Maybe because the parts where Galileo is doing science or where he is dreaming the future leaven it sufficiently. Maybe because the drama played out over the Copernican world-view is compelling. Maybe because the drama played out near Jupiter is compelling and towards the end an imaginative and descriptive triumph that brought tears to my eyes.
People who have read a fair amount of KSR will know that he has a strong theme of environmental concern running through most of his books. It's back again here but it is mixed with questions about the effect of science and religion on society, whether human nature will evolve, the consequences of war, the compulsive nature of the scientific mind, the beauty of nature and what constitutes life.
A pleasure to read, building steadily to a dramatic climax in Rome and on the moons of Jupiter.