Andy Burrows is midway through a self-mocking sketch about his unlikely rock star lifestyle – pool parties in LA, writing in Kate Hudson’s piano room – when Matt Haig puts down his beer and interrupts.

“Don’t follow Andy on Instagram,” he chuckles, “because he’s always having a better time than you.”

“But internally I’m having a shocker,” Burrows replies. “I look at my Instagram and go: ‘My life’s absolutely incredible; why am I in such a shit state?’”

You can see how the pair gravitated towards each other. In 1999, Haig was rampaging through a drunken Ibiza summer as house guest of the owners of Manumission, when he suffered a devastating emotional breakdown from which it would take him three years to recover.

“I’d had issues for years that I wasn’t addressing,” Haig explains. “I was the typical young man escaping my problems – drink, drugs, late nights. I’d been working in Ibiza for three years and just had this panic attack out of nowhere. It was a week before I was coming back to London for a round of dead-end jobs … and everything just crashed on top of me. I was suicidal. It was a pain I didn’t think I could handle. There was a long three years of trying to get to know my mind and sorting myself out.”

The traumatic episode inspired the author’s 2015 dissection of depression, Reasons to Stay Alive. And it was in this book, under a chapter entitled Self-help, that Haig wrote a simple note to self – “How to escape time: music”.

A few years later, on tour as Tom Odell’s drummer – one of his many musical outlets since quitting Razorlight in 2009 – Burrows escaped music with Reasons to Stay Alive. “It was like having an on-tour counsellor in my bunk,” he says. “We meet on the same page in terms of the psychological state that we’re in.”

“We’re totally neurotic,” Haig agrees, “a few anxiety issues.”

The marriage of rock and literature that became the duo’s first collaboration album, due in January, began with a Twitter crush. The pair followed each other in “mutual, silent admiration” for a while before Burrows, a few beers down, “slid into [Haig’s] DMs”. The artistic version of a Tinder date? “Well, he swiped right,” Haig laughs. “This is the good thing about social media. You can do things you’d be a little bit uncomfortable about doing face to face.”

Initially, Burrows thought they’d find a creative bond somewhere between Haig’s children’s fiction and his own 2012 soundtrack for The Snowman and the Snowdog. They conceived an animated fairytale noir rock opera in the Hansel and Gretel vein. When that idea faltered all seemed lost, until Haig turned to Reasons to Stay Alive and began lyricising the traumas of his panic attack and depressive disorder.

“It was my therapy notes turned into songs,” says Haig. “In a nonfiction book you have to research and fact-check everything. In a song you can just get to the essence of what you’re feeling and be raw and totally true about it.”

Having breached the barricade between Haig’s published work and the sort of stirring, orchestral, 70s-flecked rock that Haig describes as “Supertramp in rehab”, inspiration flew, Haig emailing Burrows lyrics from his “stinking duvet in Brighton” and Burrows firing back completed demos from – oh yes – Kate Hudson’s LA piano room.

“My wife’s got a fitness studio called POPfit which she’s set up with Kate,” Burrows explains, a little abashed. “I was looking after our daughters there while she set it up, and I had the best time because I had these incredible words to play with. Every night, I put the girls to bed and I had the night to myself, staying up really late in this soundproofed room.”

As Haig found himself penning lyrics about his wife Andrea’s “everyday heroism” in dealing with his depression (Hero), his recovery (Handle With Care) and the optimism he eventually emerged with (Tomorrow), the album came to earn the same title as the book. Yet Reasons to Stay Alive, the album, delves further into fiction: Parallel Lives is a musical synopsis of an unwritten novel about “a sort of suicide attempt, and between life and death he gets to live every other version of his life. That’s something we all feel, especially nowadays when we’re seeing so many other people online and so many other possibilities and we’re thinking, ‘I should be there’… We’re comparison-shopping our lives.”

This crossover of music and fiction has a recent precedent. In the wake of her 2015 album Hypoxia, which was inspired by Sylvia Plath’s The Bell Jar, Kathryn Williams was contacted by Laura Barnett, in the throes of writing her second novel, Greatest Hits. It traced the life and career of fictional songwriter Cass Wheeler over 16 songs, the lyrics of which bookend each chapter; Barnett hoped that Williams would write the songs for her character. The making of 2017’s Songs from the Novel Greatest Hits involved Williams inhabiting Cass to a degree that Daniel Day-Lewis might deem intervention-worthy.

“There’s a difference between writing the songs to fit in the book, and then performing the songs as Cass, and trying to get into the different decades of her career,” says Williams. “I didn’t get to read the book until we’d finished the album and it was a strange experience, almost like looking through a photo album because I’d already had quite a lot invested in a lot of moments in her life.”

Does a literary thread elevate the humble album to a higher art form? Burrows admits to Haig’s input making his music feel “a bit classy”, but Williams argues otherwise. “I love the immersiveness [of literature] – once it’s inside you, it can echo out when you’re reminded of it in your life. But I have songs that have been special to me for 30 years, and they walk alongside you in your life. Songs that are important to me and remind me of who I was and are still there for who I am now, I think that’s magical.”

Williams has secretly been writing her own novel, and the Haig and Burrows collaboration continues, with a more story-based second album likely. “It’s just working out what that narrative is,” says Haig. They’d better build an O2 Hay-on-Wye: lit-rock is becoming a real page-turner.

• In the UK, Samaritans can be contacted on 116 123 or email jo@samaritans.org. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international suicide helplines can be found at www.befrienders.org.