Ten years ago, Richard Askwith wrote Feet in the Clouds, a celebrated tale of fell-running and obsession. It interwove Richard's's compulsive desire to finish the gruelling Bob Graham Round – a nightmarish 66-mile, 24-hour tour of Cumbria's 42 highest peaks – with historical accounts of Britain's colourful fell-running heritage and interviews with the eccentric characters who think nothing of trotting through the most inhospitable landscapes this country has to offer. If you don't know it and you are runner who reads (or a reader who runs) you'll love it, and you are in luck as an updated anniversary edition has just been published. If you do know it, then you'll be interested in Richard's second book, Running Free, which is published on 6 March.

Running Free is a joyous, eloquent and lyrical account of one man's lifelong love affair with running – and most particularly his passion for running in nature. For Richard there is no better way to spend a Sunday morning - in fact any morning - than stepping out of the back door of his Northamptonshire home and flinging himself across muddy fields and frozen streams, doing battle with nettle thickets and slippery stiles, all the while with Nutmeg his dog matching him stride for stride.

But it wasn't always like that. Richard, like so many of us, used to be a pavement pounder. In Running Free he details how he fell into running in his 20s (overweight and fed up) and grew to love hammering around the parks of the capital and along the south London streets where he used to live. He was always watching the clock, always trying to better his PBs, always clipping seconds from set distances and well-worn routes. But slowly, running became more and more about escape, about leaving the day's stresses and strains behind by, ironically, losing himself in the real world. A place of weather, seasons, nature, mud, hills, mist and more mud, lots of mud. In a defining chapter, Richard describes how he got totally lost on a rural run in France. He had no idea where he was or how to get home. He ran for miles. And slowly, without sounding at all cliched, a new reason to run dawned on him. Now he rarely times his runs. He doesn't even wear a watch. It doesn't matter how fast or slow he is going, it is all about being in the run: "mindful" running. And this new purpose brings rich rewards. Richard writes beautifully about discovering the things most of us never notice: birdsong, different types of mud (we have more than 100 words for the brown stuff), the furrows on a ploughed field, the changing seasons … In many ways Running Free is a hymn to the beauty of the English countryside.

Alternating with these pastoral chapters, Richard documents his ambivalence at the arrival of "big running" and the commercialisation of what should be the most free and liberating of all sports. As he says: "Running hasn't got any more expensive, so why are we paying so much more to do it?" His book charts how running has become monetised and sanitised; how we feel compelled to buy the right kit; how we pay £50 and more simply to run a route that we could do for nothing when ever we wanted; how obstacle events such as Tough Mudder and Rat Race, sell us a tame, anaesthetised version of adventure. He's absolutely right. Running is now colossally big business, and it really doesn't need to be.

By "running free" or as he sometimes says, "running natural", Richard taps into what the sport should be when stripped of all the consumerism and health-and-safety nonsense. He talks about the benefits of running barefoot; he becomes a human "hare" and is chased by a pack of dogs; he goes cheese rolling; he joins a "man hunt" – a sort of extreme version of cross-country tag. His book is a love letter to running outdoors in all its many forms, and there is plenty of it out there, enjoyed everyday by countless thousands. Running Free is simply the prod you need to make you step off the pavement and into the wild. The book is also practical. It tells you how to defrost frozen toes and how to run through a herd of cows, how to pick your way across flooded fields and over slippery styles.

While Feet in the Clouds was driven by the narrative of whether he would finish the Bob Graham, this book is slower and gentler. It's happy to meander its way through a lifetime of jogging. It drifts in parts and I did find myself skipping over some of the natural descriptions, lovely though they are. But mostly I had the heart-lifting sensation that I was out there in the mud with Richard and Nutmeg, running free.

Running Free: a Runner's Journey Back to Nature by Richard Askwith is published by Yellow Jersey Press on 6 March, price £16.99