At the beginning of The Passenger, Cormac McCarthy seems to have taken a turn for the literal. For nearly six decades, McCarthy’s great twin themes have been the brutality underpinning the American myth of the West and the human longing for salvation in an apparently godless world. Here, then, is the protagonist of his new novel, a professional salvage diver by the name of Robert Western. Point taken. The book begins with Western on a job, investigating the fuselage of a private jet submerged in the Gulf of Mexico. In the depths, Western finds the rudiments of a promising mystery: no apparent crash damage, a missing flight recorder and one passenger unaccounted for. The scene seems set for a thriller along the lines of No Country for Old Men (2005).

No chance. The mystery, if that’s what it is, remains mysterious to the end, unexplained either by Western or by the spooky government agents who occasionally show up to search his lodgings. We learn a bit about Western himself, though: he’s a whizz-kid physics dropout, a former racing driver and the son of a Manhattan Project nuclear scientist. His father’s occupation and his mother’s Jewish ancestry embed Western in the history of human violence that is McCarthy’s familiar preoccupation: ‘Auschwitz and Hiroshima, the sister events that sealed forever the fate of the West.’ Later, in flashback, we observe Western digging hundreds of thousands of dollars in antique coins out of the concrete basement of his grandmother’s house. (Where did the money come from? Another mystery the novel doesn’t care to solve.) And we follow him, between jobs, as he wanders through the streets and lounges of 1980s New Orleans, shooting the breeze with a supporting cast of misfits and barflies on subjects ranging from the Vietnam War to the history of quantum theory and trying to figure out what kind of mess he’s gotten himself into. As the net seems set to close in, Western goes on the lam, holed up first in a tumbledown shack on the Mississippi shoreline, then in a frigid Idaho farmhouse in the depths of winter.

The Passenger is a great sprawling scrapyard of a novel, and it’s hard at times to shake the suspicion that its many dead ends and digressions have themselves been salvaged from some deep reservoir of unpursued drafts and then patched together – an enterprise given coherence by McCarthy’s characteristic evocation of a world in which obscurity is an existential constant rather than merely a literary atmosphere. Part of the difficulty is that some of its most surprising passages sound less like the McCarthy we know than like his idiosyncratic contemporaries. For most of his career, McCarthy has had to contend with comparisons to his most obvious precursors, Faulkner and Hemingway; in The Passenger he more often seems hellbent on sounding like his peers. There are parts that have the ring of Don DeLillo (‘Information and survival will ultimately be the same thing. Sooner than you think’). Lunching in a Mafia-owned joint with a New Orleans private eye, Western listens to a conspiratorial riff on the Kennedy assassination that might have been ripped from the pages of James Ellroy. And moments of Pynchonesque vaudeville pepper the narrative by way of the hallucinatory visits of a band of sideshow freaks, led by the punning Thalidomide Kid, to Western’s schizophrenic sister Alicia, a mathematical prodigy.

In the companion novel, Stella Maris, these hallucinations fall away, making room for Alicia Western’s own story: her mathematical gift; her unrequited, incestuous love for her brother; her gradual journey towards the act of suicide that removes her from a world in which she sees no meaning or order except in the laws of mathematics (no spoiler here: her hanging body appears on the first page of The Passenger). Consisting solely of dialogue between Alicia and a psychiatrist at the sanatorium where she has had herself committed (the Stella Maris of the title), this novel is briefer and more intimate than The Passenger and all the better for the restraint. It’s tempting to call Stella Maris the superior book, but these stories are so mutually interdependent as really to comprise one novel split unevenly (and lucratively, one imagines) across two volumes.

Psychology in McCarthy has always been something implicit, to be inferred from behaviour and speech. Yet even by these standards, Alicia is a thinly sketched presence, less a character than a mouthpiece translating the familiar Old Testament manner into a new mathematical idiom:

Assuming at last that one could, what would be the advantage of ignoring the transcendent nature of mathematical truths. There is nothing else that men are compelled to agree upon, and when the last light in the last eye fades to black and takes all speculation with it forever I think it could even be that these truths will glow for just a moment in the final light. Before the dark and the cold claim everything.

Part of the power of the Pulitzer Prize-winning The Road (2006) came from its unexpected quietude. It was as if, in imagining a world beyond the collapse of civilisation, McCarthy had been compelled to modulate the higher frequencies of his epic style. Similarly, these new novels are at their best when the prose is tempered by the rhythms of speech, as when Western, dispatched to an oil platform out in the Gulf of Mexico, tunes in to the almost liturgical rhythms of the drillers’ jargon, or when, beyond all the quantum theory in the conversations with her psychiatrist, we begin to glimpse the sources of Alicia’s troubled psychology. Not that McCarthy offers any resolution, of course, for her or for the reader. In his world, as ever, some things are simply beyond salvaging.