Ganymede hopes that Galileo will aid his campaign to stop the Europans from entering the moon's subsurface ocean and communicating with the intelligent entity that inhabits it.

Hera warns Galileo that he will be burnt at the stake unless he comes to understand the events of his life better--in particular, his interactions with women and the privileged position he has occupied in a patriarchal society.

Through futuristic technology, Galileo relives his relationships with his domineering mother and his mistress Marina Gamba, as well as other events of his life.

Ganymede injures the Europan intelligence, believing that contact with a vastly superior entity will throw humanity into existential despair.

[10] Adam Roberts described the book as an homage to Johannes Kepler's Somnium, sometimes identified as the first science fiction novel.

[7] Writing in The Guardian, Alison Flood noted that Galileo's Dream was the first of Robinson's novels to feature time travel or aliens.

[3] The media studies scholar Sherryl Vint published an article about the novel in the journal Configurations, putting it into dialogue with ideas from science studies and Fredric Jameson's conception of utopia: "Just as Galileo shows readers what is valuable in continuing to see the sacred in the natural world—a perspective lost by the story we tell of the scientific revolution—so Hera and her amodern ideologies show Galileo that science was never separate from the social world of patriarchy.