When Canadian author Ann Walmsley’s friend first asked her to help her with a book club at a men’s prison, it felt as if a grave had opened up beneath her.

Eight years earlier, she had been strangled and violently mugged outside her Hampstead home, just two months after moving to the UK from the United States.

It was a terrifying experience from which she had still not fully recovered.

But her writer’s curiosity outweighed her fears about coming into such close contact with criminals again, and the result was The Prison Book Club, which documents her experiences reading and discussing books with inmates who had committed some unspeakable crimes.

“It was the best thing I ever did,” Walmsley reflects. “I think I was living more fully more completely during those months when I was in the book club than ever before in my life, apart from maybe at the birth of my children.”

The book follows Ann as she nervously attends book club meetings at Collins Bay Institution, a medium security prison near Toronto.

It’s far removed from her book clubs back in Hampstead, where she was a member of the Literary Ladies and another, smaller club.

Instead of wine and cheese, at Collins Bay there’s just frank discussion of classic works of fiction and non-fiction: from Mark Haddon’s The Curious Incident of the Dog in the Night-Time, through Margaret Attwood’s Alias Grace, to John Steinbeck’s Grapes of Wrath.

And rather than middle class women who have English literature degrees, these book club members were convicted drug dealers, fraudsters, armed robbers and even murderers.

“It does feel like more is at stake with a prison book club,” says Walmsley. “For them, they see each book as self-improvement, as an opportunity to get a leg up.

“You can see that longing, which perhaps you don’t see as much in our ladies’ book club, where we take for granted that there will be intellectual stimulation and social sharing. There, it doesn’t feel like: ‘Wow if I go to my book club this evening, I might be able to change my life.’”

Any preconceived notions of how criminals with limited education might discuss a book are set aside as soon as you read about the first session that Walmsley attends.

The men’s insights are nuanced, intelligent, and often more thought provoking than the readings offered by the volunteers from the ‘outside’.

Despite their criminal pasts, they are preoccupied with judging characters to be right or wrong, and their confinement leads to in-depth analysis based on close readings.

“What I expected was that, with my English literature degree, I would be pointing out interesting things to them. But I found that more often than not, they were pointing out interesting things to me,” Walmsley says.

Though they prefer non-fiction, the inmates also relish picking up a novel.

One of their favourites while Walmsley was volunteering was The Guernsey Literary and Potato Peel Pie Society.

This tale of another book club, set up out of desperation by the residents of Guernsey as a way of surviving the island’s Nazi occupation, spoke to the prisoners.

“Books are a great leveller,” Walmsley adds. “When we read, it wasn’t an inmate reading with a volunteer from the outside, it was two people being excited by a protagonist or plotline and discovering things in the book that they are showing the other person.”

By the end of Walmsley’s account, reading has not only helped rehabilitate some of the inmates, but Walmsley too.

When the book was first published in hardback last autumn, she went back to Hampstead for the first time since leaving in 2005, re-visiting one of her old book clubs where, ironically, the group discussed Walmsley’s work.

Whilst in Hampstead, she decided to test herself by walking past the scene of her old attack, outside her old home in Cannon Lane.

“I actually felt ok in the day time,” she says. “But I had to walk home from the book club to the tube station to get back to my hotel.

“Because of all the news of the recent attacks, I asked my friend’s husband for a drive to Hampstead station. I still wasn’t sure how things were.

“I really felt disappointed in myself because I felt I had come so far with the men.”

Walmsley may still be left with post-traumatic scars from her horrifying attack, but she is left with no regrets about her time with the inmates.

“I was left feeling that my father was right. If you expect the best of people, they will rise to the occasion.”

The Prison Book Club is published by OneWorld in paperback, £8.99. Walmsley will be in conversation with Piers Plowright about her book at Burgh House in Hampstead on June 2 at 7.30pm. Tickets £12 including a glass of wine.