The date of Vincent’s death suggests even more desolate contexts: Li gave several interviews early that year, promo­ting her essay collection Dear Friend, from My Life I Write to You in Your Life , in which she coolly dissects her own mental collapse, which included two suicide attempts. “It was the year of my disintegration,” Li’s “mother” writes in Where Reasons End. Later she adds: “I was almost you once, and that’s why I have allowed myself to make up this world to talk with you. Sadness one can live with, but sadness is a helpless garrison against the blindness of tragedy.”

“The blindness of tragedy” is a phrase to conjure with (the correct Li would doubtless prefer “with which to conjure”). What follows is a wide-eyed attempt to stare her tragedy in the face. The resulting book exists in an artistic universe light years removed from the melo­dramatic emoting of misery memoirs, the glib solace of self-help or even the twists of a psychological thriller.

For one thing, the big, if obvious question, that so often shapes these narratives – why does Nikolai commit suicide – does not intrude upon Li’s text. Her “mother” does not set out on a crusade to excavate Nikolai’s reasons. His death is simply an ineluctable fact, however heavy that weight might be for his mother to bear from one moment to the next. “I’m not as sad as you think,” he says evenly. “Not any more.”

Why then summon Nikolai into her imagination in the first place? This question is frequently raised, if never granted an easy answer. Nikolai must, in a literal and liter­ary sense, be composed, made up and born again if only through language and not in a sentiment-risking mind’s eye. It’s as if Li is inverting the act of sacred creation to make the flesh word. “It was not a world of gods and spirits. And it was not a world dreamed up by me; even my dreams were mundane and landlocked in reality. It was a world made up by words and words only. No images, no sounds.”

This Nikolai in words emerges as a precocious, possibly brilliant child – a poet or a novelist or an editor in waiting – almost as demanding as his mother when it comes to saying what he means, or insisting on the same rigour from others. When his mother thinks, “Sometimes what you make up is realer than the real,” Nikolai shoots back: “The dictionary would disagree with your statement.”

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The character of Li’s maternal proxy is also concentrated, whittled back to basics. Denied a name, she is “mommy”, as if Nikolai’s death has eclipsed all her other identities, which are glimpsed in flashes: wife, cook, friend and mostly reader and writer, whose exacting, rather intimidating linguistic fastidiousness bears more than a passing resemblance to that of Li herself. This crescendos with an actual mention of A Thousand Years of Good Prayers (2005), Li’s first published story collection, on page 75 of my copy.

Li has always been a writer whose genius tends towards the finely rendered miniature. Her literary peers are poets such as Elizabeth Bishop, whose Argument gives this book its nuanced title (“all the way to where my reasons end”), and short-story writers including Li’s beloved William Trevor. One feels positively unkempt in its presence – as if one’s in a lift wearing sweaty gym clothes beside that fussiest of dressers, Hercule Poirot.

But here, Li’s prose is even more spare and pared back than usual: “No images, no sounds.” “Deadline as a word used to fascinate me, a word that connects time and space and death with such absoluteness,” Li’s “mother” says, for example.

Such precision gives a reader pause. This is not a book to be hurried, but one whose words demand close attention. Take that Elizabeth Bishop-quoting title. Where Reasons End suggests both Nikolai’s explanation (for suicide) and his mother’s – for writing the book and perhaps for going on living. Haunting both interpretations is “reason” singular: a loss that verges on madness, no matter how reasonable Li tries to sound.

Where Reasons End, it is safe to say, is not an easy read, and not only because of the harrowing premise. The challenge has little to do with Li’s vocabulary, which is relatively simple, or her intent, which strives to say exactly what she means. But there are moments when her desire to commune with her departed son risks both narcissism and finickiness, charges she acknowledges herself. “A neat dream is all about self-indulgence,” Nikolai berates his mother after she describes several about him. If Nikolai is simply Yiyun Li ventriloquising her real son, then he is no less affecting for that. One inescapable conse­quence of his departure is this is all she can do – talk to herself and hypothesise what Nikolai might say.

Yet here is where art in general – and literature in parti­cular – offers, not consolation or solace, but a response: a place where impossible communion can occur. Nikolai may be a fiction, but that is no small thing. “One never makes things up in fiction, I said. One has to live there as one has to live here. [Nikolai says] Here is where you are, not where I am. I am in fiction, he said. I am fiction now. Then where you are is there [the ‘mother’ says], which is also where I live.’

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A passage like this might sound impossibly calm, ultra-rational, but in the context both of Li’s grief and her narrative, they are white-hot with feeling. “Would you call [my death] a tragedy,” Nikolai asks. “I would only say it’s sad. It’s so sad I have no other adjectives left,” Li’s “mother” replies. Everything is touched by Nikolai’s death – his juvenile poems, unfinished stories, the trees on the street. What isn’t written is as poignant as what is. At one point Li’s “mother” translates a Chinese poem into English. It begins: “When I was young I knew not the taste of sorrow.” The second, and final stanza, sums up this austere, forbidding but profoundly beautiful book better than anything I can offer:

“Now I have known the taste of sorrow

and want to talk about it, but I refrain

I want to talk about it, but I refrain

And say merely: a chilly day, what a fine autumn”