The novel tells the story of Leigh, a young girl who grows up in the Netherlands amid the specter of climate change and eventually becomes a marine scientist exploring ocean trenches and investigating an anomaly at the edge of the solar system.

During her research trip, she and her team are tasked with testing a remotely operated underwater vehicle developed by NASA that they hope to one day deploy to explore the oceans of Jupiter's moon Europa.

In a review for The Guardian, Adam Roberts stated: "The whole novel is beautifully written: richly atmospheric, full of brilliantly evoked detail, never sacrificing the grounded verisimilitude of lived experience to its vast mysteries, but also capturing a numinous, vatic strangeness that hints at genuine profundities about life.

"[5] In The Observer, John Self stated: "The mystery of where Leigh will end up is so enticing that it's a shame when the last substantive section of the book returns us to Earth and family life, with a thud of crammed backstory and a few future shocks.

"[7] Writing for The Times Literary Supplement, Beejay Silcox praised MacInnes for his insightful depiction of different characters in the book, stating: "In Ascension finds as much poetry in the human microbiome as it does in the grand revolutions of the planets.