SINGAPORE - One day in September when he was 24, British author Matt Haig went to the edge of a cliff in Ibiza, Spain, and considered throwing himself off it.

It would have taken him a few steps forward. In the end, he turned and walked away.

Every summer that passes takes him further away from that moment, says Haig. "I have always liked marking that passing of time, because every age I reach is an age I never thought I'd get to when I was suicidal.

"I was 24 years old and I didn't think I would live to be 25. I never thought I'd be 30. I'm 45 this year. It's amazing and it's a great way to cope with getting older because I thought I'd never be here, so everything is a privilege. To be alive is a privilege."

Haig is the author of some 20 books, but the one he remains best known for is his 2015 best-selling memoir Reasons To Stay Alive, in which he opens up about his battle with severe depression and the mental breakdown that almost led to his suicide.

His new novel, The Midnight Library, is the closest he has got to representing his own experience in fiction.

Nora Seed, 35, lonely and depressed, decides to kill herself, but at the stroke of midnight finds herself in a library between life and death, where each book on the shelf is a chance for her to explore another life she could have had.

She could experience the life in which she became an Olympic swimmer, for instance, or the one in which the band she and her brother formed became a global phenomenon, or even the one in which she was an Arctic glaciologist.

She must find the right life to settle down in, even as time, however mysteriously it works in the library, begins to run out.

"I've always been fascinated by parallel lives," says Haig over Skype from his home in Britain, where he lives with his wife and two children aged 11 and 12. "A library is sort of like a place full of parallel lives, where you can escape into different worlds."

Libraries have a special place in his heart. When he was growing up in the small English town of Newark, where there was no cinema, no bookshops and nothing to do, he would spend his afternoons in the great glass library at the centre of town.

"I didn't always have a great time at school," he says. "Being able to just sit in this giant green-house of a library was great."

If there was ever a time to write a book championing libraries, he adds, it would be now.

"In England, as in quite a few places in the world, libraries aren't particularly valued at the moment and their budgets are being cut. And because this year has been so devastating for the economy, I think libraries are going to suffer even more.

"I think there's a misconception that because of the Internet, we don't need libraries any more. But libraries are about so much more than just going to get a book. It's important to have these public civic spaces. They're also important for democracy and accessibility because not everyone can afford to buy every hardback book they want and not everyone can afford to study."

Not everything Haig writes is about mental health.

His many books include The Last Family In England (2004), a reworking of Shakespeare's Henry IV Part I, but told by dogs; The Radleys (2010), a young adult tale about middle-class vampires; and How To Stop Time, his 2017 novel about a man who has been alive for more than 400 years.

What connects his protagonists, he says, is that they are all outsiders.

"I'm always careful never to just write about mental health," he says.

"I try not to stay in the lane of depression. But also the act of writing and talking about depression is actually helpful to me in itself and because it's brought a lot of people to me, which has made my own mental health journey feel less lonely.

"I think one of the subconscious reasons I started writing about depression was that I wanted to feel less weird and strange, because when I became ill when I was young, what was dangerous about it was that I felt totally alone. I thought, no one has felt like this. Of course, that's not true. Lots and lots of people feel like this."

These days, everyone seems to be trying to bring his books to screen, from an adaptation of How To Stop Time produced by and starring Benedict Cumberbatch, to the upcoming film A Boy Called Christmas, a reimagining of the Father Christmas story.

Reasons To Stay Alive has been turned into a television drama by British broadcaster UKTV.

Haig describes attending a screening last year as "a very weird experience, almost like being on drugs".

He recalls: "You're watching yourself, who's not yourself, go through the worst time of your life... It was quite an intense hour and I came out with a headache."

Even though it has caused him so much pain, he would not choose a life in which he did not have depression. "If given a choice to press a button that said, 'You've never had depression or a panic attack in your life', I would not press that button.

"I have honestly known more happiness this side of being mentally ill than I ever did before, as a young adult or child. And I think that is because of my experience, which has made me more grateful and look after my mental health."

He is now working on a non- fiction book with the broad title of The Comfort Book, which he says assembles bits and pieces of comforting quotes and advice that might be helpful to readers, given the ongoing Covid-19 pandemic.

"This year has been particularly stressful for everybody," he says. "And I always try and write the book I would most want to read at that point in time."

• The Midnight Library ($29.95) is available at bit.ly/MidnightLibrary_Haig