As you might be able to tell from the choice of title, Markus Zusak's latest novel Bridge of Clay features a motif that feels particularly timely. Not to spell it out too much but, set against the West's increasingly polarised political climate, bridges stand as a symbol of the compromise, cooperation and unity that are sorely needed though all but non-existent. However, don't let yourself be fooled: Bridge of Clay is far from media cycle fodder tagged to current events.

Although a basic sketch of its themes – masculinity, fractured families, the natural world – seems to dialogue with prescient contemporary topics, the novel was written over a process of two decades. In fact, the intricate and beautifully characterised Bridge of Clay is something of a magnum opus. 'It was the idea I was always a bit afraid of,' Zusak explains. 'I kept pushing it away, writing other books in between, until the time came after The Book Thief, when I thought, Now you have to face it.'

Given its lengthy gestation period, it's unsurprising that Bridge of Clay is largely a book about process: the process of building the eponymous bridge as much as that of pulling together a story. Focusing on the lives of the Dunbar brothers as they recover from their mother's death, the novel traces youngest sibling Clay's painstaking bridge-building alongside eldest brother Matthew's retelling of the family events that give shape to the book.

The way that the bridge and the family history slowly take shape is mirrored in the act of reading itself, with the story unravelling itself with each page – never handing things to the reader readymade. 'I often say to people that it's a story where you can only fully understand the protagonist (and his family) by reaching the very end,' Zusak explains. 'Each step is one more piece that leads to that understanding.'

Taking a fluid approach to time as it traverses different generations, Bridge of Clay allows you to step outside of the ticking clock of notifications and news alerts characterising the incessant speed of today's world. An advocate of delayed gratification, Zusak muses that 'novels are one of the final sentinels that tell us we don't need to know everything straight away.' Elaborating, he explains, 'The story and characters in Bridge of Clay reveal themselves slowly, the way most of us do in order for people to truly know us.'

With this expansive approach to time, It's fitting that Clay is never described with a phone in his hand – a detail that allows him to take on a timeless quality and, according to Zusak, shows that he's concerned with the kind of struggles that can't be resolved with a quick Google search. 'He's a character that refuses the trappings of the modern world. He's locked in battle with a challenge that has been going on in humans forever – to reach for something greater than he can actually achieve.'

Zusak might be involved in the business of writing fiction, but he knows that through this vehicle that he's able to access these more elusive truths – the realities about how things have come to be the way they are, or what we want our place in the world to be – that can only be accessed by piecing together moments of the past. As he so succinctly puts it: 'We fictionalise to tell the truth: we use fiction to tell us who we are.'

Markus Zusak, Charlotte Square Gardens, 12 Aug, 5pm, £12 (£10). Part of the Edinburgh International Book Festival.