At first sight, J — which has beenshortlisted for the Man Booker Prize — represents a significant departure for Howard Jacobson. It’s set in a future Britain where some sort of apocalypse — known only as ‘WHAT HAPPENED, IF IT HAPPENED’ — has taken place several decades ago. It also contains virtually no jokes. Yet, from within this unfamiliar framework, some familiar concerns soon emerge.

In 2010, The Finkler Question was hailed as the first comic novel to win the Booker since Kingsley Amis’s The Old Devils. But the book darkened considerably towards the end, with Jacobson unsmilingly warning his readers — and especially any fellow Jews who regard such warnings as ‘hysterical’ — about the continuing, potentially lethal dangers of anti-Semitism.

At one point, with the cultural boycott of Israel gathering pace, a woman finds herself suddenly frightened as to where the protests against her Jewish museum might lead. ‘It was hard to picture herself as a deportee in a thin floral dress, carrying a little suitcase, her eyes hollow with terror,’ she reflects, ‘as she strolled through St John’s Wood with her jewellery clinking.’ But then again wouldn’t the Jews of 1930s Europe ‘have found [their] fate hard to picture too’? After seeing a ferociously pro-Palestinian play (obviously modelled on Caryl Churchill’s Seven Jewish Children) another character goes even further, believing that ‘there’d be no settling this until there’d been another Holocaust’.

Well, in J, there has been — perhaps not on the industrial scale of the Nazis, but effective enough. And, as we slowly learn some of the details of WHAT HAPPENED, IF IT HAPPENED, it’s evident that Palestine was indeed part of the reason — or, more accurately, part of the excuse.

The main characters are Ailinn Solomons and Kevern Cohen, a couple who’ve recently fallen in love, and whose surnames might seem to indicate their racial background. Except that one of the ways the authorities have tried to restore social stability — and increase the confusion about what happened, if it did — is by making everybody take Jewish names. Only gradually do the pair discover that they’re ‘the real McCoy’, Ailinn when she finds some letters home written by her grandmother Rebecca as a young woman, not long before the pogroms began in ‘201-’. In them, Rebecca argued firmly — but as it turns out wrongly — that her parents’ anxieties about growing anti-Semitism were simply paranoia. (In the early 20th century, remember — as Jacobson presumably does — it was often German Jews who were most dismissive of the Zionist idea that the Jews would never be safe in Europe.)

As ever, Jacobson serves up plenty of literary riches here, adding a particularly deft plot to his usual qualities of close analysis and endlessly good phrasemaking. Sentence by sentence, he remains perhaps the best British author around — and even the absence of jokes doesn’t preclude lots of zinging one-liners. (‘When everybody’s feeling the same thing it can appear to be reasonableness.’) I finished the book, in fact, convinced that I’d just read a masterpiece.

The trouble comes with reflecting on it afterwards. Once you’re not being swept along by Jacobson’s prose, the awkward realisation dawns that he’s not joking, in more ways than one. Nor is he merely trying to write a work of dark fantasy. For the novel to carry the kind of punch he clearly intends, it needs to be at least imaginable that, within the next few years, the British people could rise up against the country’s Jews, who still occupy ‘a particular, even privileged place in the nation’s taxonomy of fear and loathing’. And that once they had, the crime could be buried. And that British Christians still define themselves against the Jews.

Personally, I can’t imagine a novel based on the premise here being any better done. Nonetheless, for a book like this fully to achieve its aim, that premise has to be believable — and in J, for all Jacobson’s skill, it isn’t quite.