Before Joanna Cannon became a bestselling novelist with The Trouble With Goats and Sheep and Three Things About Elsie, she was a doctor specialising in psychiatry. In Breaking and Mending, she brings her literary talents to her previous career in a memoir brimming with her trademark compassion and psychological insight.

In the opening chapter, Cannon sets out one of the core themes of the book, like the opening of a Bach prelude and fugue to which she will return in various ways throughout the following pages: “We imagine, strangely, that they [doctors] are invincible… [we] hold on to the belief that a doctor has the power to save us – and if they are unable to save themselves, what hope does it offer to anyone else?”

Over the course of her training and early medical career, Cannon discovers not only that doctors can be as vulnerable and fragile as their patients, but that sometimes those vulnerabilities make for better, not worse, medical professionals.

An early chapter titled Wild Cards describes how Cannon came late to medicine. Having left school at 15 with a single O-level, she worked in pubs, restaurants and department stores: “But I never lost a vague and quiet hope at the back of my mind that one day I would return to education.”

The theme of wild cards is another that permeates the book: Cannon is acutely aware that she has not followed a conventional path, yet what comes through potently is how often it is this “wild card” status that made her such a good doctor.

Perhaps it is because she has not enjoyed a lifetime of privilege that Cannon is so attuned to other people’s stories and that she finds diagnoses in the spaces where other doctors might not look. While many of her medical school peers hoped for a career in cardiology – “when it comes to kudos, heart trump brains, brains trump bones, bones trump skin” – Cannon was always drawn to psychiatry.

“Lives can be saved by spotting something lying hidden in a history,” she writes. “Lives can be saved by listening to someone who has spent their entire life never being heard.

“I learned that returning a life to someone very often has nothing to do with restoring a heartbeat.”

But Cannon is not so naive as to think that kindness and compassion are straightforward acts. Early on in her training, she learned that empathy can sometimes be misplaced when she tried to reassure a cancer patient by referring to her father’s illness. She writes: “You really can have the wrong kind of kindness. Kindness isn’t a one size fits all.”

Given that Cannon is no longer a practising doctor, there is inevitably the story of why she left the profession. She writes eloquently about her admiration for the NHS and about her frustrations with the bureaucracies that eventually drove her away from it.

She explains: “You quickly find that you can never be the doctor you wanted to become, because the doctor you wanted to become would not be able to survive.”

In the past few years, there has been a plethora of medical memoirs. What sets Cannon’s book apart is not just its humanity and wisdom but the novelist’s keen observational eye. Cannon is a chronicler both of the human condition and the quotidian details – the clothes, the tics, the sights, sounds, smells and ephemera – which speak to who we are.

While the medical profession’s loss may be publishing’s gain, one cannot help but wish that the NHS might be filled in future with doctors just like Cannon.

• Breaking and Mending by Joanna Cannon is published by Wellcome Collection (£12.99). To order a copy go to guardianbookshop.com. Free UK p&p on online orders over £15. Phone orders min p&p of £1.99