A few years ago, the Irish author and critic Paraic O'Donnell went viral on social media after devising a game called "book review bingo". As the name suggests, he created a bingo card with various "common refrains" of literary criticism on it, and readers could then have this to hand while working their way through the books pages of their weekend newspaper of choice.

One of the expressions O’Donnell included was "searingly honest", and when it comes to writing about memoirs this is indeed a classic cliché – so frequently deployed as to have become almost meaningless. And yet, and yet... it's also an entirely appropriate description for John Niven's new book, O Brother.

For something to legitimately qualify as searingly honest, it should make you mentally flinch, almost as if somebody were holding a red hot branding iron against your skin. Not many books can do that, but Niven’s does, not just because he’s honest about events that occurred, but because he’s honest about his thoughts relating to these events, even the very darkest of them. The moment of maximum flinch comes towards the end, where he is reflecting on the suicide of his younger brother, Gary, at the age of 42. There is, he writes, something he and his sister Linda can only whisper to each other, "the thing unsayable when it comes to the suicide of a difficult, troubled sibling... I'm glad he's dead."

John Niven PIC: John Phillips/Getty Images

The story of how Niven reached this point is laid out with the same degree of truthfulness over the preceding 350-odd pages, and – as you'd expect from the author of novels including 2017's No Good Deed (which The Scotsman praised for "probing dark, uncomfortable areas of the male psyche") – it is ferociously sharp on the contours of both brotherly love and brotherly rivalry. While Niven left his working-class 1970s Ayrshire childhood far behind, first working in the music business in London, then becoming a successful novelist, Gary (“Shades" to his friends) stayed in Irvine, sold drugs, went to jail, suffered ill-health, became increasingly irrational and finally alienated everyone who loved him, to the point where he couldn't think of any reasons to carry on.

Of course, there's much more to it than that: Niven is disarmingly candid about his own failings, his late father's difficult relationship with his youngest son, and clear-eyed, too, about how Gary's refusal to conform, while ultimately contributing to his downfall, was also part of what made him so charismatic, and – in spite of everything – so loved.

In the end, there’s a sense that all this painful truth-telling might also be healing, so perhaps it’s only half a cliché to describe the honesty in O Brother as both searing and cauterising.

O Brother, by John Niven, Canongate, £18.99. John Niven is appearing at the Edinburgh International Book Festival on 23 August.

Book review: O Brother, by John Niven