Novels with plots that are slight or familiar-seeming tend to compensate by pumping up the idiosyncrasy of the narrative voice. Even the most humdrum events become interesting, if the person telling us about them is a “character” of some definite kind: amusing, monstrous, self-deceiving, knowingly unreliable, even just quirky.

This is certainly what seems to be on offer in John Banville’s The Blue Guitar, of which the title, which nods at Wallace Stevens, warns us to expect a cubist approach to “the truth”. In fact, its plot contains very little in the way of surprise or novelty (man has affair, runs from beloved when rumbled, has guilty fit, reunites with wife – who has also been carrying on elsewhere – is diminished, and finally becomes the caretaker of former beloved’s ancient dog), and the manner of its telling is no more daring. Although Banville’s narrator, Oliver Orme, articulates a gradual descent from sprightliness to gloom cleverly enough, he does so without any significant artistic sleight of hand. He provokes his fate, suffers it and writes it down. He’s a straightforward sort of sucker.

He is also cultured, digressive and, in his way, charming, a roly-poly Dylan Thomas type – but Irish, and without the genius – who introduces himself with apparently minimal embarrassment as a lapsed painter and a still-active petty thief (very petty, as it turns out). He might also have added narcissist and self-analyst with a special interest in exploring the connections between the various elements of his existence. Just as he tried to bridge the gap between “things in themselves” and their artistic representation in his painterly days, so now in his thieving and in his adultery he takes from one reality to establish another.

Since these attempts all lead Orme to failure and disappointment, it is fair to say that his story has a tragic dimension. And yet we don’t feel it as such in any compelling way. Orme’s narration is too chattily affable for that, too intent on deflation and self-mockery. Besides, he is too much of a klutz. Does this mean that Banville, who is generally so skilful at showing the sufferings of the human heart in love, wants us to withhold our sympathies in this case? It seems unlikely. More probably, by making his main character a familiar kind of fool and not a figure of gigantic anguish on a blasted heath, he intends that his readers will identify with him more readily.

And we do identify, of course – but the restrictions are there. The modesty of scale cannot be denied. Especially since the downsizing that affects Orme himself also applies to others caught up in his debacle. Gloria, his wife, is a “preternaturally composed” and largely absent figure – a water-colour character among the oilier others. Polly, the object of his affections, is (at least to start with) a jolly, pink-cheeked country girl with “something childlike” about her. Her husband Marcus is a likable but wet repairer of watches. The local grandee Freddie is a mild-mannered toff from central casting. None of them, in other words, is able to act as a sufficiently extensive canvas on which Orme can project his largest human feelings. Neither are they smart or canny or ironical enough to offer him other ways in which to express these things.

The same might also be said, albeit in different terms, about the setting in which all this takes place. Orme has returned to where he spent his childhood – an unidentified Irish town in which the landmarks are as generic as the inhabitants (big house, studio, gatehouse, fish-and-chip shop). But any hopes that he might cherish of being stimulated by these old connections to take up his paintbrushes again are already extinguished by the time we meet him. In fact, it is partly as a result of feeling like “a familiar alien” that he flirts with Polly, and so precipitates the “grotesque bedroom farce” of the plot.

At every turn (and the structure and setting of the book are very tight, so there aren’t many turns), The Blue Guitar leaves us in the hands of a character who wants to think big thoughts about the mess he has made of things, but who struggles to rise to the occasion. He cannot even think amply, healingly enough about what he believes is the root cause of his present waywardness – the death of his daughter in early childhood, which has turned his own and his wife’s present life into “aftermath”. As for the waywardness itself, there is the same self-knowledge but the same peculiar government of the tongue. In life and in love Orme cannot connect with himself; the original vagueness of his temperament has mutated into paralysing uncertainty; focus has become selfishness; engagement has become wearily passive acceptance. And what’s the conclusion? “One does what one does,” he sighs, “and staggers bleeding out of the china shop.”

• Andrew Motion’s The New World is published by Jonathan Cape. To order The Blue Guitar for £11.99 (RRP £14.99) go to bookshop.theguardian.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min p&p of £1.99.