The Atlantic Ocean, by Andrew O'Hagan

Storm warnings for this leaky union

Two women, West End posh and shipyard wifie, are waiting for a Glasgow bus, and making defensive small-talk. "Where are ye gaun for yir holidays?" says the wifie. "Bermuda." "How d'ye manage that?" "My husband works for Cunard." "Ma man works for Cunard tae, but we dinnae get to places like that."

Sancho Panza country: Andrew O'Hagan watches the sludge boats, south of Ailsa Craig, discharge Glasgow's solids, while giving pensioners a comfy voyage. We called them "banana boats", Dr Freud, and they looked like steam-yachts. They emphasised civic fundamentals, like sewage farms. Edinburgh ran Festivals and pumped its ordure raw into the Forth: "What Edinburgh spends on powdering its nose, it saves on wiping its bottom."

The Atlantic Ocean, O'Hagan's "essays on Britain and America", inherits this pugnacity. The republican unionism latent in Scots Catholicism marks the opening review, of Neal Ascherson's Stone Voices. O'Hagan denounces as typically Scots the anti-gay campaign launched against the first post-devolution ministry, ignoring the Daily Record's frantic English editor, Martin Clarke.

O'Hagan's Atlantic, viewed from Irvine on the Ayrshire coast, seems comparatively elusive. "My Grandfather's Ship" has the dry detail of Irvine novelist John Galt, inventorising the SS Montrose, which ferried and trapped the murderer Dr Crippen. But where's that sense of weather, time and faraway embodied in Conrad's sad Judea in Youth: the log-line of mental distance? Where's any reference to that other, weird if temporary, Atlantic Irvingite, Edgar Allan Poe?

O'Hagan doesn't flatter, and nationalists can't afford to: Scots are older, fatter and sicker. Alex Salmond has currently conjured up a politics of movement, but he has yet to detach his nation from the big beasts – the welfare state, the big bank, the multinational, the supermarket – that have sheltered it since war-driven industry collapsed in 1920. O'Hagan's first book, The Missing, meditated on the Thatcher era, the undernourished nestlings shaken away to oblivion. His 1993 essay "On Begging" spiritually belongs there, Orwell's shadow distinctly visible. Fragile Scots have felt that way for four generations.

O'Hagan is a materialist, into what Henry James – on Trollope – called "squalid realism". A good post-Catholic vocation: think of hard men like Joseph MacCabe, Robert Tressell, Willie Gallacher. In The Missing, people dematerialised. Here, "The Death of English Farming" shows how secure nursery-school things like sheep, cows, fields become worthless. "The Garbage of England" shows rubbish recalibrating wealth.

Such essays, more than half the book, are conceptually dense, their questions searching enough to compel comparison with Henry Mayhew. Could O'Hagan produce another London Labour and the London Poor, with all its risks? In "After Hurricane Katrina", he leaps the pond and lands poised, playing on such painful engagement. Sam and Terry, its poor white, and beaten black, protagonists, go west on a mercy mission to New Orleans, get so close to Orwellian decency, then are severed from it by the yahoo language of sexual execution. Compared with this, O'Hagan on UK culture sounds like "This is the way the world ends, not with a bang but a giggle".

Post-modern irony beats up the usual suspects – Posh, Becks, Di, Jordan – and their dump-bucket careers. He could be dissecting the mentality, digitalised by cash, of the New Labour delirium: the ghosts paid by the literary machine, the tabloid bravoes. They're probably as bored by football as O'Hagan or me: pilgrims in the barren land surveyed by another angular Scot, AL Kennedy: "In Britain we are self-revenging. We take on our own destruction."

Documentary and drama in O'Hagan are curiously insulated from each other. In his fine long essays a constant spiky presence is that of his revered ES Turner, Tory literary gent and nailer of quackery, snobbery, dim-witted pretension. He should take Turner's cue and do a Zola on a scale to match the UK cacophony: his anti-heroes, the dwarves who felled The House of Reith. He has the skills, the distancing, the laughing savagery for it.

Christopher Harvie is an SNP member of the Scottish Parliament and author of 'A Floating Commonwealth' (Oxford)