Beatrice Leigh is a nurse, an evangelical Christian, a cat owner and “an independent and capable woman”, not necessarily in that order. She lives in a Britain perhaps not so far in our future, in which “institutions that have been around forever are going to the wall” and a collapsing economy and deteriorating climate have become indices for one another. It would be easier for Bea if she had her husband Peter’s support, but he can’t help: he’s trillions of miles away, on a planet called Oasis, with a mission to convert its alien inhabitants. The conversations of Bea and Peter, which scaffold Michel Faber’s astonishing and deeply affecting sixth novel, are held via a kind of interstellar email. The awkwardness of this medium amplifies to screaming pitch our sense of the emotional space between them. “Sometimes,” she tells him angrily, “I feel as though your leaving caused things to fall apart.”

Peter, meanwhile, finds it hard to focus on anything but his situation. The jump between worlds causes him to hallucinate. Oasis is too much to take in. His mission is financed by and carried out under the auspices of a shadowy corporate called Usic. They need him but won’t say why. The base personnel describe themselves as “a community”, “in partnership” with the indigenous population – “we do not use the word ‘colony’ ”. Yet many of them specialise in oil and mining technology, and Usic is already building infrastructure to support a larger population. Trade has begun, although it has taken a weirdly localised form: the Oasans produce food for the human settlement; in return, they seem to want only Earth analgesics and the Bible, the eponymous “book of strange new things”. On being shown a picture of Peter’s pet cat, they ask if it’s a Christian. When he tells them that, though he loves it anyway, the cat can’t be a Christian because it’s an animal, they respond: “We also love those who have no love for Jesus. However, they will die.” Finding a way through these mysteries requires Peter, whose Christianity is never presented as less than honest, to identify and dismantle his own deep temperament – avoidant, confused, manipulative, mistaking obsession for commitment.

Like every fiction of Faber’s, The Book of Strange New Things is determined not to be mistaken for any other fiction written by Faber. At the same time, it’s difficult to read the description of an alien face as “a placenta with two foetuses – maybe three-month-old twins, hairless and blind – nestled head to head, knee to knee”, or an energy-saving lightbulb as “a segment of radioactive intestine suspended from a wire”, without remembering the hallucinatory intensity of work such as Under the Skin. Oasis is a strange world, half paradisal, half dull, prime real estate for the imagination realised with determined sensuality. The atmosphere is full of “the sound of agitated leaves”, although there are very few leaves anywhere. The rain tastes sweet. The Oasans always wear gloves, and hooded pastel-coloured robes made of a fabric “disconcertingly like bathtowel”. When they try to pronounce an “s”, they make the noise of “a ripe fruit being thumbed into two halves”.

This is a big novel – partly because it has to construct and explain its unhomely setting, partly because it has such a lot of religious, linguistic, philosophical and political freight to deliver – but the reader is pulled through it at some pace by the gothic sense of anxiety that pervades and taints every element. Earth is becoming untenable. The more he feels at home with the Oasans, the more guilt Peter feels at abandoning his wife. The Usic personnel – who think of themselves as outcasts, members of a foreign legion – seem self-repressed to the edge of explosion. The Oasans, with their inexplicable faces and obsession with sharp objects can’t, surely, be as simple, gentle and fragile as they seem. And has their language, literalistic to the core, caused them to make a basic mistake about the Christian promise of eternal life? Even the planet’s low-diversity ecology seems to harbour some tension in need of resolution. The reader is desperate for relief, which can only come from turning another page, and then another and another.

In Peter’s quarters at the Usic base, he finds “a red button on the wall labelled EMERGENCY, but no buttons labelled BEWILDERMENT”. Equally lost in the wild, dragged on by a mounting sense of urgency, we dread some upshot both ironic and gruesome: but while its surface finds the comic in everything from corporate architecture to the communication of taken-for-granted religious concepts, the deepest levels of the book privilege directness over irony. What you see is what you get: humans and aliens patiently trying to dismantle the very concepts of human and alien; making contact, making the best they can of a bad job. “We need a certain proportion of things to be OK,” Bea tells Peter, “in order to be able to cope with other things going wrong.” Perhaps that’s all we can ever hope for.

Meanwhile, we have their letters, full of heartbreaking chat and a growing anger on her side, and on his a kind of restless evasiveness as he tries to find her life as interesting as his own. He misses her desperately, but he’s charmed and overwhelmed by all the strange new things; alone with everything they used to handle as a couple, she’s increasingly frustrated and desperate. The tragedy is that while we know that, Peter doesn’t. If he spends the novel lagging behind the edge of the present, Bea spends it trying to stay ahead. She’s less concerned with understanding than keeping her head above the water. History is happening too fast and too completely for them. But what begins on Oasis must end on Earth and if Peter sets out as a holy fool, God requires him to finish as Orpheus. “I hear rain again. I love you and miss you. Don’t worry about anything.”

• M John Harrison’s Empty Space is published by Gollancz. To order The Book of Strange New Things for £14.99 (RRP £18.99) go to bookshop.theguardian.com or call 0330 333 6846.