As if America does not already have enough problems, a Sinclair Lewis revival is going on. Within a week of the November 2016 election, Amazon had sold out of Lewis’s novel It Can’t Happen Here, first published in 1935.

Senator Berzelius ‘Buzz’ Windrip, the novel’s protagonist, is a crass nativist who wins an election by stirring up resentment of immigrants and the press. Once in power, he turns dictatorial. He imprisons his enemies, sets a militia on his subjects and builds a detention centre on the campus of Dartmouth College – an idea with which anyone who has tried to hold the attention of American college students for fifty minutes will sympathise.

To confirm the improbability of Lewis’s scenario, the hero of the resistance is a journalist. So are many of the would-be heroes of the resistance who have hailed Lewis’s novel as a warning of where Donald Trump’s presidency is likely to lead. It’s so hard to keep up. Last year, we were meant to avoid literature likely to trigger feelings of anxiety and persecution. This year, we are meant to seek it out.

Two other warnings from the first half of the 20th century, Nineteen Eighty-Four and Brave New World, have also been undergoing a revival in popularity. Between the day of Trump’s election and the day of his inauguration, 47,000 copies of Nineteen Eighty-Four were sold in America, 36,000 more than were sold in the equivalent period twelve months earlier. After the inauguration, Kellyanne Conway’s quip about ‘alternative facts’ inspired Penguin to print another 75,000 copies.

The tide of miserable prognosis has also lifted the undeserving boats of Steinbeck’s The Winter of Our Discontent (1961) and Hannah Arendt’s The Origins of Totalitarianism (1951). Arendt’s work is not technically fiction, but when you read her apologia for Heidegger or the chapter where she attributes the rise of the Nazis to British policy in South Africa in the 1890s, you know it has the makings of a comic novel.

The novel as warning is a regrettable by-blow of the 19th and 20th centuries. The earliest examples contained warnings of a general kind: A Tale of Two Cities warns against fanaticism, War and Peace warns against invading Russia, Madame Bovary warns against adultery. None of these warnings resembles the desperate allegories of Zamyatin’s We or Koestler’s Darkness at Noon. But then no 19th-century government approached the awfulness of the 20th-century dictatorships.

You can see the change in Orwell’s novels. His early novels are always warning against something in the 19th-century way – exploitation, industrialisation, low-grade sausages, working in a bookshop – but he only goes the whole hog in Animal Farm. Many readers of Orwell agree that Animal Farm and Nineteen Eighty-Four are not his best novels. But quality, as the Sinclair Lewis revival shows, is of secondary concern to many readers. The literature of warning succeeds if it incites political outrage. We read it not to change our minds but to confirm our prejudices.

This is why the most influential warning in modern fiction is not a technological dystopia like that of Margaret Atwood’s MaddAddam or an old chestnut from the 20th-century literature of totalitarianism. It is the racist fantasia of Jean Raspail’s The Camp of the Saints (first published in France in 1973). In the early 1970s, Raspail spent his summer holidays at his aunt’s house near Cannes. Looking at the Mediterranean one day, he imagined ‘that the Third World would rush into this blessed country that is France’ and wrote what he believed was a warning. In Raspail’s novel, the wretched of the earth cram onto boats and sail to Europe. The resulting crisis is as much humanitarian as moral. The Europeans do not want the immigrants, but they cannot refuse them, especially when the television cameras are watching and the Pope is pontificating. Like the last of the Neanderthals and the bankers of Davos, the white Europeans retreat to the mountains of Switzerland.

Since it first appeared in the USA in 1975, The Camp of the Saints has found a cult following there. Cordelia Scaife May, sister of the philanthropist Richard Mellon Scaife, funded its republication in 1983. May was also a supporter of anti-immigration activist John Tanton, whose Social Contract Press itself republished the novel in 1994 and 2001. Steve Bannon, now President Trump’s chief strategist, has referred to the book several times. In October 2015, he described the refugee influx into Europe as ‘almost a Camp of the Saints-type invasion into central and then western and northern Europe’. When the Breitbart Book Club is launched, The Camp of the Saints will no doubt be one of its first offerings.

Rather than read the books that feed our anxieties or flatter our prejudices, to really understand what is going on we should perhaps turn our attention to those that politicians read. Theresa May, who recently discovered that she did believe in Brexit after all, says that Pride and Prejudice is her favourite book. In his last weeks in office, Barack Obama admitted that his foreign policy had sought to disprove the opening lines of V S Naipaul’s A Bend in the River – ‘The world is what it is; men who are nothing, who allow themselves to become nothing, have no place in it’ – and that reality had often tended to vindicate Naipaul.

Some people think that Donald Trump is an oafish philistine who cannot read more than 140 characters at a time, but this is an unfounded calumny. Speaking to an audience at Liberty University, a Christian college in Virginia, in January 2016, Trump remarked, ‘The Bible blows them away. There’s nothing like it, the Bible’ (The Art of the Deal, though, runs it close). And in June last year, Trump told the Hollywood Reporter that he was rereading All Quiet on the Western Front. Quite a lot of people get blown away in that one too. We can’t say he didn’t warn us.