His neighbours dismiss him as “a complete and utter oddity”, but if you’re a Patrick McCabe fan you’ll recognise the main character of his latest novel. Pat has been around since The Butcher Boy as abused son, bullied schoolboy, village scarecrow or anarchist, the bright-enough child beaten into the darkness of his own bent imagination by the cruelty of dysfunctional parents and an uncaring community. You’ll recognise versions of the brutish father, too, and a mother whose violent emotions swoop between sentimentality and hate.

If, like the author, you grew up in an Ireland struggling between De Valera’s old, anti-materialist ideals and the bright promises of the modern world, you’ll remember quaint publications like Emerald Gems of Ireland. Through the late 1950s and 1960s, their blurry newsprint lined up beside the shiny new titles of the day to recall the disappearing songs and stories of some kinder age.

Cleverly, McCabe has fitted his novel into that faded literary frame, so rendering his sudden passages of gore and mayhem all the more colourful when they appear. Pat McNab is an innocent, pulled back and forth between those extremes of old and new Ireland. Tales of his disillusionment, of sweet optimism dashed again and again by the selfishness of the real world, are strung together in unchronological order like the rough “gems” of those forgotten magazines.

Insights into Pat’s horrible childhood, adolescence and middle age are set between the mawkish songs of heroism and love that have helped shape his dreams. The disjunction between reality and the cosy old images of small-town Irish life set the scene for Pat’s descent into madness. Beginning on his father, our hero becomes avenger, dispatching his adversaries into eternity “like they were the shite of fleas ... a sack of good for nothing germs!”

Language is shaped to serve the author’s bitter wit. He uses a multiple narrator, who lurches between naturalism and pretension, like the writers of old Emerald Gems. At one stage, Pat’s face becomes so taut with fury “it was as though he possessed a length of carpet for a mouth”. As more and more dead bodies feed the laurel bushes, Pat’s predicament is compared to Macbeth’s: “I am in blood stepp’d in so far that, should I wade no more, returning were as tedious as go o’er.” Elsewhere, knowing archaism is used, as when the killer steps out into a morning “spreading its gossamer cloak across the countryside”.

Like Pat’s darkening imagination, some horrific scenes are lightened by memories of film. Disinterring his mother’s disintegrating body to sit with her “in the warmth” suggests another more famous mammy’s boy. Did Psycho inspire Pat to kill? Or simply to dress up in his mother’s wedding dress when dispatching some of his victims? Certainly, a peyote trip into border territory is delivered in the jerky style of spaghetti westerns; but a long sequence in which Pat captures a bagful of money from some gun-slinging gangsters travels beyond the dreamworld of Bonnie and Clyde to a chilling reminder of the real-life murderers who operate just a few miles from him in Northern Ireland.

Yet there is no chance to reflect. A relentless comic narrative sweeps tragedy aside. Often it is delivered as brilliant one-liners, but it can slip between irony and slapstick, as when a black American baddie tries to shake down the local drapery store. Having felled him with a baseball bat, the old Irish proprietor informs him that “this ass-mother ... was shakin’ shook in Brooklyn when you was knee high to a culpepper coolshank!”

Yet for all its quirkiness and ventriloquism, the novel’s structure fails to satisfy. The changing narrator and Pat’s unchronological history create a maze that even the most persistent reader might find difficult to follow. Also, by beginning in the middle of McCabe’s (already familiar) psychosis, the build-up of tension as each new experience accumulates upon the last is never allowed to develop. Instead we must examine the varying texts as psychologists, picking out small germs of truths from so many falsehoods.

In that, the sharp-eyed reader will be rewarded. Evidence that seeps between funny digs and fantastic nastiness makes McCabe’s continuing thesis about the deep-laid ambivalence of Irish life all too clear. The parody of voices that once peddled old fictions about Ireland’s “difference” as a nation of saints, scholars and comic songsters may amuse those who can remember them. But the raw fury with which they are mocked is not funny at all: these fake gems are splattered with real blood.