Garth Greenwell is best known for autobiographical fiction about sex and the body, but with Small Rain, the American author now turns to the physicality of suffering. In sparse prose interspersed with occasional lyrical musings, a nameless poet is diagnosed with a small tear in his aorta, which results in a long stay in a clinic, where he shuffles from the ER to the ICU.

A strange pain takes over his life, becoming “a kind of environment, a medium of existence”. This is the first of Greenwell’s novels to be set in the US, in a hospital in Iowa. Set against the beginning of the Covid pandemic, it asks poignant questions about care, connectivity and community. What do we owe one another in “the project of being a human being”?

Greenwell is fascinated by our collective performance of morality. In Cleanness (2020) this often concerned questions of consent, nationhood and student-teacher relationships. Small Rain explores the need for platonic touch amid the depersonalisation that medical institutions require. A hospital novel offers a perfect setting to explore the body in a new context – the narrator compares one procedure to the experience of doing poppers. The poet’s time inside is slow and agonising, as Greenwell zooms in on the minutiae of care. His life is ruled by doctors whose names he can’t recall; “the pain defied description”. Some nurses are nicer than others, he discovers. Not everyone recognises the humanity of those in their care.

The body is the medium of Greenwell’s humanism. Through intimate descriptions of hands on shoulders and prodding needles, he explores how to overcome the meaninglessness of pain – not through ascribing morality to sickness, but through our response to it.

Greenwell approaches the pandemic through a variety of perspectives: nurses struggling to make ends meet, their conspiracy-theorist uncles, siblings who don’t always wear masks. The consequences could be severe if the immunocompromised narrator contracts Covid. Still, he tries to navigate the world lightly. When his sister doesn’t always mask around him, he realises he has a choice – to connect with her and take the risk, or to prioritise his own care. Greenwell doesn’t valorise this decision; Covid isn’t a crisis about personal choice, but about community. These interlacing vulnerabilities are the crux of Small Rain. When a nurse is kind and breaks the facade of professionalism, the narrator wells up.

At times, he feels a kind of moral paralysis. He watches the 2020 Black Lives Matter uprisings on TV and thinks about the Trump supporters in his family. Political discourse is “that weird intellectual weather”. He tries to shield himself from the ideologies of separation, wondering how we can come together despite our differences. Sometimes this reads as a bit too romantic, leaning heavily into an amorphous ideal without touching on the history of disability and vulnerability.

Before he goes into hospital, the protagonist and his lover, L, are in a rhythm, or perhaps a rut. They work in the same house, in different rooms, every day. Sometimes the narrator wishes he could leave the stability of his teaching job and travel again. He goes on long digressions about how, when he bought the house, a storm nearly destroyed it. Community plays a part in this story, too: the people who come to check on him after the wind abates; the arborists who deal with the trees. These digressions, he realises, are part of life. These, and poetry, of course. He performs an extended reading of George Oppen’s poem Stranger’s Child. He attempts to steer his students away from “making a poem a puzzle they could solve”.

Small, redemptive moments make life worth living. “Commonness didn’t cancel wonder.” A Snickers bar is a source of wonder, playing with a dog in a park is marvellous, the way lovers fit together is magical. “Maybe everyone feels the way I do,” the narrator thinks, “that it takes an act of will to hang on to a life.” Provisional truths, the marks of happiness, the nearness of death: these open us up. The doctors tell the narrator to move on, to treat his time in the hospital as an accident on the road of life, but of course pain leaves a mark too. Suffering’s monotony isn’t noble, Greenwell suggests, but something that teaches us how to live nonetheless.

• Small Rain by Garth Greenwell is published by Picador (£18.99). To support the Guardian and the Observer, order your copy at guardianbookshop.com. Delivery charges may apply.