Her latest novel has just been Radio 4’s Book at Bedtime and a screenplay is in the pipeline. So is life serene, 24/7, for Meg Rosoff ? Not quite.

%image(15417656, type="article-full", alt="Meg Rosoff and lurchers by the North Sea. A day like this is absolutely horrible in London. It really is especially where we are now, where there arent any trees. Grey and dirty, ugly and grim. Whereas here its luminous. Photos: SIMON PARKER")

However, much we try to pretend we’re immortal, most of us finally concede that life hangs by a thread. Meg Rosoff is a born-again horse-rider. Was a born-again rider. Always pretty fearless, she’d taken it up again a few years ago and had refused to be deterred by a number of falls that left her concussed. Until last year, when a bad tumble left her lying unconscious in a field for 20 minutes.

She was on “a horse I probably shouldn’t have been riding, but it’s so impossible to say no to an amazing horse. Too much for me”.

Meg eventually came to. She had her phone, but – dazed – couldn’t think who to call. “No names in my head...” Finally, she went through texts and found someone she thought she could ring. Afterwards, “I realised I couldn’t afford to have any more concussions – I’ve had a few, and it really affects my memory – but also the way I came off... I don’t remember exactly what happened.

“The last thing I remember was the horse bolting to the end of the field. She either stopped short or she turned sharp left; either way I could so easily have broken my neck.

%image(15417657, type="article-full", alt="Author Meg Rosoff. I thought God, my careers going slightly... a bit less every year. My books arent naturally populist. Theyre a bit difficult for teenagers... they dont quite hit the major adult market'")

“I just thought ‘I’m fearless, but I’m not stupid. I am stupid, but I’m not that stupid. So, yeah, I miss it. It was like an addiction. And I’ve been thinking that, since I’m here, I’m maybe going to go up to Poplar Park and just groom.”

“Here” is coastal Suffolk.

It’s a cold and blustery day by the North Sea – the firewood popping, snapping and spitting, refusing to play ball in a living-room lacking central heating – but it’s still easy to see why the author is spending more time at her beachside bolthole.

%image(15417658, type="article-full", alt="Meg Rosoff did one more brief rewrite on Jonathan Unleashed and her agent sent it out. 'Nobody had been desperately enthusiastic about it, but then it just went "Bworrrrgggh. Penguin could probably have bought it for �25,000 or something, and instead it went way up into six figures. We were all shocked'")

The view across the shingle is austere but beautiful. Squint and you can make out Orford lighthouse in the distance, still just about standing upright on the ness.

“We’re so in love with it. Still. A day like this is absolutely horrible in London. It really is – especially where we are now, where there aren’t any trees. Grey and dirty, ugly and grim. Whereas here it’s luminous.”

U.S.-born Meg has co-owned this cottage with her best friend for more than a decade and comes up as much as she can. She was staying here when inspiration alighted three summers ago and she woke up with the first line of her next book in her head. It’s a bit of an odd one:

“Jonathan came home from work one day to find the dogs talking about him.”

%image(15417659, type="article-full", alt="Meg Rosoff's new book - first novel for adults; first comedy - Jonathan Unleashed")

“I thought ‘I must write that down.’ And then thought ‘I don’t have to write that down. I’m not going to forget it.’ I forget everything, but I knew I wasn’t going to forget that.”

Jonathan Unleashed – her first novel for adults, and “a flat-out comedy” to boot – is out now. It’s a departure for a writer whose books thus far have been categorised as “young adult” and been pretty dark or challenging.

Debut story How I Live Now, for instance, saw urban punk Daisy dispatched to the English countryside from New York to stay with her aunt and cousins. The Third World War breaks out, the children’s familiar worlds are turned upside down, and they face a fight to survive.

The book has sold more than a million copies in three-dozen or so countries, was shortlisted for the Orange First Novel Prize and was made into a film in 2013, starring Saoirse Ronan.

Five books that followed either won awards or were shortlisted for them. But it still wasn’t enough to quieten the ever-present angst that dogs many a creative type. The film had its admirers, but was never going to be a blockbuster.

“If you live in London, every time you go onto the Tube there are six new films promoted on big posters. Of those, you never see or hear of five and a half of them again. They come and they go; sometimes in a weekend. And there’s no such thing as a slow-burn now,” Meg says.

It did boost book sales, though. “I remember Anthony Horowitz saying to me that no matter how badly a film does, you’ll sell 200,000 books. Well, I didn’t. I probably sold 20,000 (extra ones). Or maybe 50,000. I don’t know. He was talking about Stormbreaker, I think, which is a completely different kettle of fish.”

Her last book, “which I really loved, just disappeared here. Completely. It is very edgy, but it is a very ‘quiet’ book.”

Picture Me Gone featured a sensitive 12-year-old girl with the ability to “read” easily-missed signs and hear the unspoken words of the adult world. That, and the rest of Meg’s work, is chalk and cheese compared with Unleashed. Dreamer Jonathan Trefoil, who works in advertising, has an unhinged boss and a girlfriend who wants to marry someone just like him – only richer. More organised. With a different sense of humour. His flatmates – his brother’s dogs: border collie Dante and spaniel Sissy – are determined to sort out his life. Sort of.

It’s a very filmic story, and it comes as no surprise to learn a screenplay has already been commissioned. Was it a deliberate strategy to write a light-hearted, visual, tale?

“I did think maybe I should write more of a film, but I can’t really set out to do anything. My brain tells me what to write and I write it. I’m not very good at premeditating anything.

“I went two years writing nothing and then woke up one morning with that first line in my head and knew instantly that was the book – even though I didn’t know what the book was. I was so excited.”

Except publisher Puffin turned it down because it wasn’t a children’s book, she says, and stablemate Penguin rejected it as an adult novel. “I thought ‘God, my career’s going slightly... a bit less every year’. My books aren’t naturally populist. They’re a bit difficult for teenagers. They’re YA books (young adult), so they don’t quite hit the major adult market. In fact, my best readers, in a way, are creative writing students!” says the author who describes herself as “moderately known”.

“I thought ‘I can’t change the books – because I’m writing exactly what I want to write – so maybe I should just think about a different way to live.’” One thought was: rent out the family home in north London, move to France or Italy, “we’ll go and do something cheaper and we’ll live off the rent and not worry so much about the pressure to write books”.

New Year’s Day, 2015, found her trawling the web, looking for a flat for a friend who had just moved to London, and up popped a photographer’s loft in Borough. “I absolutely fell madly in love with it, even though my husband and I” – the painter Paul Hamlyn – “didn’t know where Borough was...” South of the river, in the heart of Southwark, and minutes from London Bridge station, apparently. Hardly any distance from the National Theatre, Shakespeare’s Globe and The Old Vic. In the heart of things, really, and enough to salve her jadedness with the capital. So a plan was hatched to downsize from Highbury.

As the sale went through, Meg did one more brief rewrite on Jonathan Unleashed and her agent sent it out.

“Nobody had been desperately enthusiastic about it, but then it just went ‘Bworrrrgggh’.” She makes the sound of an explosion. A good explosion.

“Penguin could probably have bought it for £25,000 or something, and instead it went way up into six figures. We were all shocked. Because you don’t know. It’s a bizarre job.”

The couple moved in June and then had summer in Suffolk. They’re here much more, now that daughter Gloria is at university. With no garden in London, now, the lurchers are much happier by the sea, too.

Jonathan Unleashed is pretty autobiographical, isn’t it? “Definitely. But I think you would have to say that about every book I’ve written. And that’s why that coming of age theme keeps coming back. Jonathan in some ways is more literal and about that period in my 20s when I lived in New York City and was utterly, utterly clueless. I was so clueless for so long,” says Meg, who grew up in a suburb of Boston and moved to London in 1989.

“I worked in advertising for more than 15 years and kept getting fired. Any sane person would have said ‘Look, this is just not for me.’ But I kept trying harder and harder and harder, thinking ‘I can crack this’.”

To be precise, it wasn’t really “being fired” but being made redundant. “I wasn’t the only one being made redundant – but I would say with greater frequency than a lot of people. And it was generally for insubordination and having a bad attitude. Which I patently had.

“It makes a lovely story now, but at the time it was really dispiriting. I kind of knew I was smarter than a lot of the people I was working with, but it seemed to be the wrong kind of smart...

“Working in an office, for morons, is what I think most of us do. I didn’t know how to deal with it. That’s why I got fired all the time. I tried to be good, but I just couldn’t do it!”

Meg was in her mid to late 40s when she published her first novel. A re-evaluation of life, following the death of her sister through breast cancer, prompted her to finally write a story that had been swirling in her head. Behind her work is a quest for self-realisation; “the process of discovering identity”.

And so began a literary second-career. Mind you, the fear it could all end tomorrow forever lurks.

Little wonder a part of her was thinking “We need a comedy.” That and being depressed at the state of the world. Why? Well, the thought of Donald Trump being elected U.S. president, says Meg, who with dual citizenship can vote on both sides of the Atlantic.

She wonders if she’s simply suffering from “old git syndrome. I’m 59 now and maybe it’s what people do when they get to be 59; they go ‘Aww, in my day, people cared...’” – particularly as her 23-year-old godson said he was not at all pessimistic about the future and was shocked she was.

“That may be our age: that sense you’ve seen it happen before, and optimism tends to fizzle. But (American cognitive scientist) Steven Pinker says there’s less violence. We have had an amazing life, in terms of peace and prosperity. And what do we do? We complain!

“I had a revelation recently that what’s ruined us all is the Christian belief that man is good and sin is deviant, whereas I think, probably – biologically – we’re bad. And that we’re always going to be bad,” she laughs.

Does the approach of 60 weigh on her mind?

“Oh god! I don’t much like the idea, though I have been getting happier as I’ve got older, so I shouldn’t complain too much.

“I think we’re going to go walking in the Himalayas for a month, so I don’t have to have a 60th party! But, yes, 60 feels old. Especially since our whole generation is so immature. We’ve never really accepted being grown-ups. We’ll go straight from adolescence to dementia!”

• Jonathan Unleashed is published by Bloomsbury at £14.99