When I met Brad Pitt after the premiere of 12 Years A Slave in Toronto, he urged me to continue doing something I don’t need encouragement to do: ‘Keep on reading.’ I read a lot, fiction and non-fiction, novels and historical monographs, books on art and books of learning. I always have, as a child, as a historian and as a journalist. One of my favourite writers is the Roman Pliny, who wrote his Naturalis Historia back when all knowledge could fit into one book. Another is the Surrealist French poet Francis Ponge, who showed in his prose-poem Soap you can never know everything, not even about a piece of soap. But seldom have I read a book that had such a profound effect on me as Solomon Northup’s account of the long years he spent as a slave in America’s Deep South.

I came across it when I was browsing the internet. The edition I saw was not very appealing — a beige paperback with a generic cover. When it arrived, I opened it without expectation. After a few pages that all changed. It was like reading Homer’s Odyssey but also like Dan Brown’s The Da Vinci Code; a story so gripping that I could not stop. I read walking, I read cooking, I read getting the children to bed and most of all I read in disbelief. How could this have happened?

I ran up the steep stairs of our Amsterdam home to find Steve in his room (he does not like to call it a studio), surrounded by books and children’s toys. As usual he was on the phone. But when he saw my eyes wide and my cheeks flushed, he hung up. ‘You have got to read this book,’ I said, speaking in capitals.

‘I think I’ve got it. You can stop searching. Everything is in here.’ Steve tried to take the book from my hands. ‘You can’t have it until I finish it.’

I had ordered 12 Years A Slave together with a bunch of other books on slavery to help Steve with his research. It was the winter of 2009. Steve had made Hunger, his first feature film, was working on Shame, which would become his second — I wasn’t involved with either — and started thinking about a third, a film about slavery. Slavery is a subject that, as far as the movies are concerned, has hardly happened; if the cinema were our only resource for learning about the past, then we would believe that slavery is a minor occurrence, something with less impact than, say, the death of Princess Diana. More movies have been made about Spartacus, a Roman slave, than about all American slaves. Even films that are about slavery, such as Lincoln, hardly show slavery in action and seldom have a slave as a main character.

We live in Amsterdam — I was born here and Steve moved here in the 1990s — the capital of the Netherlands, a country that participated heavily in the Atlantic slave trade and was one of the last to abolish slavery in its American colonies. No Dutch film about the subject had been made until last year. In the centre of Amsterdam, slavery is only apparent for those who know that some of the opulent canal houses of the Golden Age were built by slave owners who made their fortune in the West Indies. Steve was already thinking about centring his film around a free man, who was American, kidnapped into bondage. He wanted a story with a main character any viewer could identify with. Then he got stuck. I had suggested he should look into true accounts of slavery. The past is an immense trove; history holds so many extraordinary stories you might not have to invent one.

That evening in his room, Steve asked me to tell him the story of Solomon Northup so far. It starts in 1841 in the state of New York, where Northup lives as a free man with his family until he is kidnapped, shipped south, sold in a slave market in New Orleans and enslaved on a series of plantations before he manages to regain his freedom in 1853. In every chapter Northup recounts something remarkable with such detail it seems time travel is possible after all. Suddenly I was there, transported from Amsterdam to Louisiana, across one continent and two centuries, to witness a lynching. His new owner wants to kill Northup: ‘ “Now then,” inquires one of Tibeats’ com-panions. “Where shall we hang the nigger?” One proposes a branch, extending from the body of a peach tree, near the spot where we are standing. His comrade objects, alleging it would break, and proposes another. Finally they fixed upon the latter.’ We had done this before, with the amazing novel Blindness by José Saramago, which was later made into a film. Steve was on the road and had left the book at home so I started reading it. Every evening he would phone from his hotel and immediately ask: ‘What happened?’ And I would tell him how far I’d got in the story that day. With Northup’s memoir we tried to do the same, but this time it was more difficult as, apart from the incredibly fast-moving plot, the book is so immersive because it is so rich in descriptions and characterisations. Every character deserves his or her own book.

Furthermore, it sometimes reads like an instruction manual for operating a plantation for sugar cane or cotton. And despite all the hardship he has to endure, Northup manages at times to be lyrical, too: ‘There are few sights more pleasant to the eye than a wide cotton field when it is in the bloom. It presents an appearance of purity like an immaculate expanse of light, new-fallen snow.’

Once you are used to the slow, somewhat grandiose style of the 19th century, 12 Years A Slave visualises history like few other books. Page after page the twists and turns astonished me. As I closed the book, I dried my tears and prised Steve from the phone again. ‘You do not have to write a script any more,’ I told him. ‘This book is the script.’ I put it in his hands, Steve started to read and soon agreed. After he finished it, the startling story of Solomon Northup became his passion.

Three years later, when I visited the set, a plantation near New Orleans, in the summer of 2012, they were filming the hanging scene. It was incredibly moving to see the effort that went into the recreation of Northup’s account, as painstaking as necessary, and as free as necessary. At the last moment Steve asked the child extras to run around in the grass behind the dangling Northup, a detail not in the book but that could well have been, to convey how cruelty formed the base of the slave system and was therefore so common children were used to it. They knew nothing else. The fact that Solomon Northup did know something else makes him unique: he is the only person who has written a slave narrative from the dual perspective of both a free man and a slave.

Every time I have seen the film, anxious in the editing suite in Amsterdam, taking notes on a laptop at home, or at the London premiere, I have nagged myself with the question: why bother? Why go through all that trouble when the book is there already? But we live in the age of the image. Photo-graphy and film have become the leading modes for seeing ourselves and the world around us. If it isn’t pictured, it doesn’t exist. Nowadays you almost need a film to read a book.

12 Years A Slave was a bestseller in its time: Northup and his co-author David Wilson’s book sold 30,000 copies in the year it appeared, 1853, a year after Uncle Tom’s Cabin. After the Civil War the book slowly faded away, until two historians from Louisiana, Sue Eakin and Joseph Logsdon, unearthed it in the 1960s. Working at the Louisiana State University at Alexandria and University of New Orleans, they established the remarkable accuracy of Northup’s account during their research. They republished it in 1968. After that it became a classic on the shelf; more revered than loved, read more by historians than by the general public.