What is a bunker? The term derives from an Old Swedish word meaning ‘boards used to protect the cargo of a ship’. But if we take it, as we usually do, to mean a defended structure, often underground, intended to shield people and important goods through a period of strife, then it is one of the oldest building types made by humans. In Cappadocia, central Turkey, there are twenty-two subterranean settlements made by Hittite peoples around 1200 BC. As their empire faltered, the Hittites dug into soft hillsides to shelter themselves. As many as twenty thousand people lived at Derinkuyu, the deepest complex.

But the word ‘bunker’ also has the scent of modernity about it. As Bradley Garrett explains in his book, it was a corollary of the rise of air power, as a result of which the battlefield became three-dimensional. With the enemy above and equipped with high explosives, you had to dig down and protect yourself with metres of concrete. Garrett’s previous book, Explore Everything, was a fascinating insider’s look at illicit ‘urban exploration’, and he kicks off Bunker with an account of time spent poking around the Burlington Bunker, which would have been used by the UK government in the event of a nuclear war. The Cold War may have ended, but governments still build bunkers, as Garrett shows: Chinese contractors have recently completed a 23,000-square-metre complex in Djibouti. But these grand, often secret manifestations of official fear are not the main focus of the book. Instead, Garrett is interested in private bunkers and the people who build them, people like Robert Vicino, founder of the Vivos Group, who purchased the Burlington Bunker with the intent of making a worldwide chain of apocalypse retreats.

Garrett calls these people the ‘dread merchants’. Dread differs from fear in that it has no object: it is fear that has not yet found a focus. And if dread is your business, business has never been better, with the sustaining structures of modern life seeming ever more fragile and challenged. The dark charisma of the bunker is probably what will attract readers to this book, but the energetic and gregarious Garrett keeps the story focused on people rather than buildings. Much of the emphasis is on his native USA, where ‘prepping’ – disaster and Armageddon preparedness – has become a significant subculture, though there are also excursions to Australia, where ecological precarity is fuelling the bunker biz, and New Zealand and Thailand, favoured global ‘bug-out’ locations of the elite.

The first wave of private bunker-building followed the Cuban Missile Crisis of 1962, during which the American government made it plain that it had no intention of providing for the shelter of more than the military and political elite. The rest of the population got the message: if the worst happens, you’re on your own. Since then, American society appears to have been locked in a spiral of mistrust. In the 1990s, religiously minded ‘survivalist’ movements sought to divorce themselves from what they saw as an increasingly controlling federal state by forming autonomous fortified communities. Alarmed at these splinter groups walling themselves up and stockpiling weapons, the government reacted with overwhelming force, resulting in multiple deaths at Ruby Ridge and at the Branch Davidian compound in Waco, Texas. This bloodshed did nothing but confirm survivalists’ worst fears.

After the 9/11 attacks, survivalism entered the mainstream, giving birth to the modern prepper movement. As bunker salesman Gary Lynch tells Garrett, 9/11 was good for business on two fronts, as some Americans began to fear further terrorist attacks while others became alarmed by the prospect of increasing domestic authoritarianism. The ‘doom boom’ has been sustained thanks to the burgeoning of such fears in recent times. Donald Trump has given a nod and a wink to the conspiracy theories that motivate militant right-wing groups, while the rise of those groups and the official indulgence of them inspire dread in others. And that’s before we get to the current pandemic.

Buried, seemingly secure, as much a target for robbers as protection against them, the bunker shares many characteristics with the tomb. Both structures mediate with a kind of afterlife: the tomb ferries the dead to the hereafter, while the bunker is designed to deliver the still-living through a period of calamity to a safer future. Hope and survival are, in theory, uplifting themes, but Bunker is, in some ways, rather depressing. The people who want bunkers have, in one form or another, given up on society, taking a dim view of its prospects and seeing it as a thin veneer of order laid over Hobbesian chaos. The salespeople naturally promote this view: ‘dread merchants’ is the right phrase for them, since dread is really the product they’re selling.

Fortunately, Garrett is a bright and buoyant guide and Bunker rattles briskly along. And he’s scrupulously fair to his subjects, mostly letting them speak for themselves. Indeed, a weakness of the book is that it is too fair to them. Fundamentally, prepping is a bleak and unpleasant philosophy. It might seem like a form of responsible cautiousness, but really it’s a bet against the rest of us; preppers don’t just want to come out the other side, they want to come out ahead. Time and again the conversation veers into conspiracies and dark mutterings with racist overtones. Garrett says that preppers often seem credulous, believing in Mayan prophecies and secret tenth planets and the like, but really they just come across as cynical. Some of them appear to be egging the apocalypse on, eager for their underground investments to pay off. Given that, it’s deeply troubling to learn that many of the world’s richest people have a sideline in prepping, getting their off-grid doomsteads in New Zealand ready. But that’s what makes Bunker a necessary read – we should be keeping tabs on what they’re up to.