"Then the driver of the car punched me in the face as hard as he could …"

Now, at the start of 2016, Amy Liptrot can tell everyone she is four and three-quarter years sober (as of the just past Winter Solstice). And when her first book, The Outrun, comes out later this month she can also say she is finally the writer she always wanted to be. Who's to say which of these is the greater achievement?

The Outrun is a memoir. It's a book about wild nights in London and different forms of wildlife in Orkney. It's full of alcohol and mistakes and anger and regret. But that's not all. It's also a clean, clear, impressive example of the new nature writing. As such, it carries a sense of astonishment at the natural world; it is a book thrilled by corncrakes and noctilucent clouds and life at the edge of the world.

You could call it an account of the getting of wisdom then; wisdom about oneself and the world around that self. Liptrot, 34, is proud of it and rightly so. But maybe, as publication approaches, there's some nerves too. "But that was the decision I took," she tells me from her London home. "To present the things that I have chosen to present."

What that includes is her family's experience of mental illness and her own memories of days and nights lost to alcohol. She reckons she was 15 when she had her first drink, at a teenage birthday party on Orkney where she grew up. "I always loved it," she admits. "I liked the changes it had on self-conscious teenagers and having this part of myself that was a contrast to the more conscientious student I was kind of appealed to me."

She's not sure there's anything particularly unusual about Orkney's relationship to alcohol. "There's the country dances and it was a big part of the discussion at school – getting blazin' and how gutted you were at the weekend. There's a teenage drinking culture in Orkney, but whether that's different from anywhere else I don't know.

"If you are an alcoholic or have a tendency to be an alcoholic you'll find a way to do that, wherever you are. It's not always the circumstances or the location. There are plenty of people who went to those dances who didn't end up with a drink problem."

Unfortunately she did. The teenager she was, juiced by music journalism and fashion magazines, had always been keen to leave the island. When she went to Edinburgh to attend university it was as much about getting away from Orkney as it was to study.

But her love of drink went with her. It was when she started drinking alone that she began to recognise that she might have a problem. "You kind of realise that's not healthy or normal. When I came back to Orkney after I graduated, during the period I was working as a cleaner and my parents were getting divorced, I certainly found drinking alone became something regular for me at that point."

It would get worse when she finally got to London. She damaged relations, lost jobs and put herself in hazardous situations with her drinking. Getting into cars with strangers for instance. That's where the punch in the face comes in. On that night things could have been much worse but for some passers-by at an opportune moment. "Your judgement is impaired when you're drinking," she says now, "and if you combine that with being emotionally distressed it can be very dangerous."

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She eventually returned to Orkney with her "tail between her legs" and trailing a sense of failure behind her. Some people have said to her that she moved home to heal herself but that's not how it felt at the time, she says. "I quit my job to go to rehab and when I came out of rehab I was unemployed. And I ended up going back to Orkney thinking it would just be for a few weeks staying with my mum while applying for jobs back in London."

That wasn't how it worked out. She was struggling with things for some time. "The first year of sobriety was really tough for me. I was wanting to drink and I was living back with my mum, unemployed."

She spent the winter helping out on the family farm but it was a job trying to locate male corncrakes for the RSPB that helped begin to turn things around for her. "That really opened a lot of new avenues to me, working with these incredibly knowledgeable people with this unusual job. It gave me the opportunities to get out around the islands at night over the period of midsummer."

In doing so she began to write herself into the landscape, find the words to describe the world around her. "I found that when I was able to take the time to understand something and observe it on a regular basis it was incredibly rewarding. Just applying my mind to things that are out with myself and bigger than myself.

The Outrun is a sensuous book, full of the summer nights and winter water. Liptrot swims, walks, lives alone on uninhabited islands and observes. And from that comes a portrait of the natural world she is absorbed into. It describes someone looking outwards after years of locking herself in.

"It gave me a sense of freedom, I suppose. I was no longer so hungover on a Saturday morning. Instead, I would be able to go out to a different part of the coastline and throw myself into the sea or spend the nights driving the roads and finding the place for myself. So it was knowledge and freedom and an appreciation of coming from a place like Orkney, I suppose. It's a bit of a cliche, but it took me going away and coming back to realise that."

She began to write about the place, posting articles on websites like Caught by the River and people responded. "My friends back in London would be seeing it and they would be so interested in my life on the farm and on Orkney. It made me realise that it was interesting and it was a bit different. And that was a big motivator in staying sober. I was producing more and the writing was better than I had done before."

Right now Liptrot is back in London after time in Berlin and thinking about traffic islands and jellyfish and greylag geese and the digital world and wondering if there's a book in it. Does she still feel defined by her relationship to alcohol? "Increasingly less so. I very rarely have a desire to drink now. That's amazing to me. I didn't know that would happen and I don't want to write about my drinking any more."

There is much more in the world to write about. But then she knows that already.

The Outrun, by Amy Liptrot, is published by Canongate on January 14, priced £14.99.

Read more: our Hot List 2016 arts picks including David Bowie and Outlander's Richard Rankin