An early “post-Brexit” novel was Michael Paraskos's Rabbitman; which was published in March 2017. This book ties together the election of “a right-wing populist” American president with Brexit. The new American president also happens to be a rabbit (which is, I suppose, hilarious). Both his victory and Brexit were the results of “Faustian pacts” with the Devil.
This takes us neatly on to Amanda Craig's novel, The Lie of the Land; published in June 2017. (Yes, note the title of this book.) In The Lie of the Land we find ourselves in 2026. At this future date, a posh couple from Jeremy Corbyn's Islington is forced to move (because of “austerity”) from London to Devon (which, the Guardian tells us, is full of “casual racists”). The author sees Devon (which is “poorer than Romania”) as a pro-Brexit heartland. Not surprisingly, Amanda Craig gives a more or less Marxist/Corbynite account of Brexit in which it was the case that “the disparities in society that led to June’s result”. (I don't know, perhaps, being superior and so utterly non-provincial, this fictional Islington couple could no longer afford three foreign holidays a year and the fees for their kids' private school – such austerity!)
This is perhaps the most over-the-top of the lot. In 2020, Douglas Board has it that a retired football hooligan wins the election! (He wins it in a “populist power grab”.) Not surprisingly, there then follows an almighty clash with the “pro-European Union metropolitan political elite”. I suppose that all the peaceful and extremely tolerant Remainers were put in concentration camps too; in which they were forced to read Mein Kampf and the Daily Mail.
In David Boyle's The Remains of the Way (yes, published in June 2017), Brexit was brought about not by the votes of 51.89% of British voters; but by an old government quango which, miraculously, still worked within Whitehall. It gets worse. This quango was set up by Thomas Cromwell under King Henry VIII. What did this quango want? It wanted a “Protestant Brexit”. In addition, after Brexit the UK suffers famines and general destitution. However, I'm not sure if the EU then supplied the UK with “food aid”, as with Michael Paraskos's Rabbitman.