A third or so into To Paradise, a terminally ill man who has arranged to end his own life through assisted dying is asked if he is scared. Not of pain, he replies. ‘I’m scared because I know my last thoughts are going to be about how much time I wasted – how much life I wasted. I’m scared because I’m going to die not being proud of how I lived.’

The sting of mortality, the craving for a legacy, the fallacy of redemption: such are Yanagihara’s preoccupations. Her 2013 debut novel, The People in the Trees, took the form of a confessional by a Nobel Prize-winning scientist – and convicted child rapist – who discovered, on a remote Micronesian island, the means to halt physical ageing. In the harrowing tearjerker A Little Life, Yanagihara’s bestseller of 2015, a glamorous clique of male friends learns that nothing can save the traumatised main character, Jude, from the terrors of his past. Yanagihara compared the story to ‘a piece of ombré cloth: something that began on one end as a bright, light bluish-white, and ended as something so dark it was nearly black’.

To Paradise, which like its predecessor is over seven hundred pages long, applies this light-to-dark formula to American society at large, as seen in three eras: the late 19th, 20th and 21st centuries. Characters are linked through time by shared names (the names of real-life American missionaries to Hawaii, where Yanagihara lived as a child) and physical spaces (in particular, a house on Washington Square in downtown Manhattan), as well as, often, Asian and Pacific heritage. Yanagihara combines an ambitious array of themes – the indelible imprint of family, the horror and clarity wrought by mass disease, the mirage of political liberation – and repeating, reconfiguring emotional threads to create an eerie, time-bending effect.

In Book I, set in an alternative 1894, a group of northeastern states, including New York, have seceded. Among their utopian founding principles is equal marriage, gay marriage having become as commonplace, seemingly, as heterosexual marriage. With shades of Henry James’s Washington Square, the plot centres on David Bingham, a cosseted 28-year-old who, to his patrician grandfather’s dismay, falls for a penniless musician – and possible con man. In Book II, set a century later in a more recognisable America, we meet Charles, an affluent lawyer, and David, his younger Hawaiian boyfriend. Charles, who is HIV-positive but healthy, and his friends, some of whom are not as lucky, obsess over how they’ll be remembered. This perplexes David and is dismissed by his friend Eden as a ‘white male fixation’. Yet David’s own fate has been shaped by cultural and familial bequests, as we learn via an extended letter from his estranged father, Wika. ‘I had wasted my life,’ writes Wika, a scion of deposed Hawaiian royalty, ‘but you weren’t going to let me waste yours as well.’

Thus far, the novel is intriguing and stylistically faultless, if somewhat lacking in momentum. With Book III, reached at around the halfway mark, it becomes unputdownable. In Yanagihara’s restrained and meticulous depiction, 2090s America is a grimly credible dystopia. Following successive deadly pandemics and with the earth’s temperature soaring, totalitarianism has been imposed. No one can enter or leave the country; gay marriage is banned and heterosexual marriage is compelled; water, food and books are strictly rationed; there hasn’t been television or internet for decades. ‘People in a young dystopia crave information – they are starved for it, they will kill for it,’ reflects one character. ‘But over time, that craving diminishes, and within a few years, you forget what it tasted like.’

Our guide to this bleak future is Charlie, a lab technician of around thirty who lives with her husband in a Washington Square flat. Charlie carries physical scars from the ‘illness of ’70’, and she is autistic (though the word isn’t used) as a result of a drug treatment, which also left her sterile. But, she explains, ‘the state had worked hard to decrease the stigmatization of sterility’. Charlie’s guileless, clear-eyed narrative voice, reminiscent of Kathy H’s in Kazuo Ishiguro’s Never Let Me Go, is Yanagihara’s masterstroke. The strangeness of Charlie’s life, with its cooling suits, protein coupons and civilian records, is made touchingly mundane, while our bygone world, which she’s learned about from her late grandfather, is defamiliarised. Washington Square, marvels Charlie, once had a fountain. ‘Over and over the water exploded and fell, exploded and fell, for no other reason than because people liked it. I know this sounds queer, but it’s true.’

Charlie’s narration alternates with letters from her grandfather, Charles, to an English friend, Peter, sent between 2043 and 2088. The two storylines build with mutually illuminating force to pose a series of interlinked questions. Does Charlie’s odd new friend, David, have hidden motives? What goes on in the house that her husband secretly visits? Is Charles, who as a scientific adviser oversaw the establishment of disease ‘containment centers’ and ‘relocation centers’, history’s hero or monster?

He, and probably Yanagihara, would say neither. Faced with the ultimate moral dilemma of whether to impose terrible suffering for the greater good, Charles decided it was unavoidable. His utilitarianism, however, had its limits and he pulled strings to ensure that Charlie, as an infectiously ill child, was treated at a hospital and not sent away. Amid the worst travails and political pressures, the primacy of human bonds is irreducible, a truth that lies at the heart of this frightening and very beautiful novel. As Charles of Book II says when remembering his mother trying, in vain, to resuscitate her premature baby, ‘I wonder who will hold that little air pump for me when it’s my turn. Not because they think it’ll revive me, or save me. But because they want to try.’