When Nadeem Aslam decided that one of the main characters in his latest novel would lose his sight, he spoke to several visually impaired people as well as to the blind.

However, he is a man of great sensitivity; there were questions he needed answers to but he could not bring himself to ask.

"By temperament – this is my character – I find it hard to talk to people if I feel I am touching a nerve," says the prizewinning, Pakistan-born British writer, corkscrewing his slight frame into an office chair in the Bloomsbury headquarters of his London publishers. "I never want to hurt someone's feelings. If they have a scar, say, I can't ask how they got it. My fear is always that I am stirring up bad memories, so I have to be careful. I couldn't ask, 'What it is like being blind? What colour is blindness? Is it white, is it black, or is it golden? What does your mind see when you can't see?'"

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Aslam's harrowing, heart-stopping, lyrical new novel, The Blind Man's Garden, opens soon after 9/11. It tells of two young men – foster brothers in love with the same woman – who journey across the border from their home in Heer, a fictional Punjabi town, into Afghanistan, where one brother is captured by an Afghan warlord, then by the US forces. Terrifying things happen to several of the characters, although they often have little knowledge as to why these horrors are befalling them. "People lie to them – they are completely blind as it were," says Aslam, who will be 47 this month, and studied biochemistry at Manchester University until he dropped out in his third year to begin writing fiction.

A gentle soul, he worked for a year on The Blind Man's Garden – which took him four and a half years to complete – before deciding to live "24/7 as a sightless person". For three weeks, over three years, he covered his eyes with cotton pads and surgical tape. "All the things I wanted to know appeared inside my head. There is a moment when Rohan [the blind man, father of one of the "brothers"] says there are coloured specks in his life, like coloured sand. I saw that! For a while it's golden, then it goes black. When it rained, I put my hand out and the first thing that came into my mind was the twinkling of stars, so I have Rohan remembering that."

There were many discoveries, continues Aslam, who is single and childless and who intends to remain so for the rest of his life, writing and living alone in London and Lahore, to which he returns every year. "It's very important to me because God is not dead in Pakistan, the way he is here."

The first time he untaped his eyes he was covered in bruises, he even concussed himself after falling over. "The third time, I was the most intelligent being on the planet! I planned everything, I drove nails into the floor in front of the cooker so I could cook at a safe distance."

He insists, in his intense fashion, that his readers don't need to know he did these things, although blindness is the central metaphor of his new book. "It's part of my research," he explains, "although I did very little for this novel. In the past I've done much more."

Aslam spent 11 years writing his second novel, Maps For Lost Lovers (2004), about honour killings, which was longlisted for the Booker Prize and shortlisted for the IMPAC, before winning the Encore and Kiriyama awards. He then had conversations with over 200 Afghan exiles in Britain for his ravishing third novel, The Wasted Vigil (2008). "It shouldn't matter what I went through to write a book because I don't matter. I am first and foremost a novelist and any amount of research, if presented ham-handedly, isn't going to convince."

And convince is what Aslam does brilliantly. He lived the life of a hermit when writing The Wasted Vigil, blacking out the windows of his brother's cottage in the Peak District, where he would sleep all day and write all night. He worked on building sites, was a cinema usher, a bin man. Yet, when he was given financial help by the Royal Literary Fund, he handed back a third because he thought it was too much, then ran out of funds. "It wasn't easy, but I was very careful," he says.

Much to his annoyance, his ascetic existence became the most interesting thing about him, taking the focus away from his remarkable work. This began with a marvellous first novel, Season Of The Rainbirds (1993), written when he "just a kid", which won the Betty Trask Award and was shortlisted for the Whitbread First Novel Award. His selfless dedication to his craft is the least interesting thing about him, he claims, adding that he regrets ever disclosing how he hid from the world and how it was September 20 before he found out about the events of September 11.

He asserts, however, that "I am a politically engaged writer. For me, the news is the most emotional programme on television. People don't understand what Pakistan went through, is going through – 30,000 people have died there in the last decade, which is one 9/11 every year. For me, the situation I want to write about comes before the characters. I always need a small amount of reality and out of that my fiction grows. But I can't make some of these things up! Why on earth would I sit down and tell of the gang rape of a child by a warlord? What kind of mind would come up with that? Google it, it's the truth! Which brings us back to 9/11. It's what I have been writing about all my life; in the Third World we've experienced small, low-level September 11s every day for years.

"We have lived through an extraordinary decade," he continues. "We went from 9/11 and the suicide of Mohamed Atta [the Egyptian hijacker] to the Arab spring and the suicide of Mohamed Bouazizi [the Tunisian street vendor, who set himself on fire], the catalyst of the Tunisian Revolution. We've had the war on terror, the call to jihad, the emergence of Afghanistan and Iraq, Guantanamo Bay, Abu Ghraib, the murder of Benazir Bhutto, the execution of Osama bin Laden, and this clash between the incomplete understanding of the East and an incomplete understanding of the West."

Go to Google, he urges, "type in 'Pakistan is -' and the autofill choices you are given are 'stupid', 'evil', 'dangerous', 'a terrorist country'. Type in 'America is -' and the choices are 'not the world',' evil', 'not a country but a business'. The logic is that there are no innocent people in a guilty nation – and this logic is on both sides. So I wanted to write a novel that would hold as many of these things as possible without it stopping becoming a novel. I wanted the complexity of one character's viewpoint placed next to that of another, the core beliefs of one Muslim against those of another. As a novelist I don't tell you what to think, I tell you what to think about. Does that make sense?"

Therefore, he believes that if his readers wish to understand what has happened in the past decade, then The Blind Man's Garden – which contains gorgeous imagery amid shocking brutality – presents powerful reasons.

Aslam was 14 when his father, a political exile, fled from Pakistan with his family. They still live in Huddersfield, where Aslam and his two brothers and sister were educated while their intellectual father worked as a bin man. "My English was very bad, so I copied Lolita by hand to learn where Nabokov placed a comma; then I copied all of 100 Years Of Solitude; then Moby-Dick so that I could see what Herman Melville was up to. I had no idea how to write – I'm still learning how to be a novelist."

No longer a practising Muslim – his mother, to whom he is devoted, is very devout, believing in the Koran's angels – his own core belief is that none of us can save ourselves, only each other.

"I will save you," he says. "Fingers crossed there is somebody else who will save me. That is how my novels work and how it is in my personal life."

He has almost finished his fifth novel, about Pakistan's blasphemy laws. "I have 11 more to write and they are all already mapped out."

They include a trilogy about Wamaq Saleem – the pen name of his beloved poet, filmmaker, Communist father. "As 'the great Pakistani poet,' he is always in the universe of my novels, of which both my parents are deeply proud. He's on page 322 of The Blind Man's Garden," he says, although the line attributed to him is actually by Simone Weil. It reads: "Love is not consolation, it is light."

The Blind Man's Garden by Nadeem Aslam is published by Faber and Faber, £18.99