One May afternoon in 2007 in Praia da Luz, Portugal, barely 48 hours before their daughter Madeleine disappeared, Kate and Gerry McCann took their three young children down to the beach. It began to rain, and the children were grumpy, but the promise of an ice cream worked its magic.
Kate and the kids sat on a bench as Gerry went over to the shop, about 25 feet away. When he called to Kate to come and give him a hand with the five ice creams, she was "momentarily torn. Would the children be OK on the bench while I nipped over? I hurried across, watching them all the time."

Life as a parent, as anyone with children knows, is crammed with such split-second judgements and (sometimes) misjudgements, so when the McCanns' story hit the press just a couple of days after that afternoon ice cream, parents all over the world caught their breath, recognising the situation. Would we have chosen to eat dinner while our children slept, unguarded, a matter of yards away? Some of us would, some of us wouldn't, but I doubt there is a parent on this earth who hasn't negotiated with their child's safety in similar ways at one time or another.

Kate McCann says her main motive in writing Madeleine was to "give an account of the truth". Given how much false information has been circulated about the family, this impulse to exert a little control excites my full sympathy. One night, exhausted and sad, she switched
on the TV for light relief, only to see a picture of her daughter with the headline "She's dead" as the following day's newspapers were previewed. The McCanns often felt that they were kept in the dark by the police, so, for all she knew, a body could have been found - but time and again, she and Gerry were forced to pick their battles, to shrug off the lorryloads of critical comment, because anything that impeded the search for their daughter had to be ignored.

Much of the comment certainly has been negative. Even now, I am not sure I understand how the McCanns came to be considered as arguidos (named suspects). Although I imagine that the Portuguese police would offer a different version of some of the events described here, no UK official believed that the McCanns were in any way responsible for their daughter's disappearance. That didn't stop the headlines and the hate mail, however, so it seems both understandable that Kate should want to take this opportunity to set the record straight and fair that she should do so.

Yet the book clearly has another reason for existing: Kate wrote it because she knew that there was a market for it. The search for Mad­eleine can continue only if there is money, and all royalties go to the fund set up in her name. With no evidence that their daughter is dead, the McCanns are determined to go on looking. Meanwhile, it's a particularly gruesome limbo they are condemned to inhabit. Kate depicts it here with chilling precision.

Before tragedy struck, this was an ordinary family. Kate tells of her happy Catholic childhood in Liverpool, where her grandad had been "chief clerk for a firm importing nuts and dried fruits". She recalls midnight feasts of pickled onion crisps and dancing to Seventies disco hits. Then came Gerry, youngest in a "boisterous" family of five, growing up in a one-bedroom tenement in Govan. Both he and Kate did well at school and went on to study medicine, she at Dundee and he at Glasgow - which is where, as junior doctors, they met.

These were clearly hard-working and driven young people. Even so, their early married years were tough. There was the hard graft of moving between jobs as he trained in cardiology. She specialised as an anaesthetist, but, wanting more sociable hours, eventually opted to be a GP. Then there was the trying - and failing - to conceive a child. I was startled to read that all three McCann children were IVF babies. Mad­eleine, their first, arrived after many attempts. "Suddenly," Kate writes, "your world revolves around this little bundle, and you don't mind in the slightest."

Madeleine is crammed with clichés of this kind, but I confess that, far from bothering me, they drew me in. Kate McCann is not a writer and makes no claims to be one - the power of her book lies in its straightforward, chatty ordinariness. It is hard, too, not to admire its complete lack of self-pity, bolstered by the McCanns' uncomplicated though sorely tested religious faith. The agony lies in the small, casual detail.

Take how, when friends first suggested a spring holiday in the Algarve, Kate wasn't keen. It seemed like a lot of effort, with three children who were so small - all that equipment to lug around. But, not wanting to spoil things, she came round to the idea. "It was the first in a series of apparently minor decisions I'd give anything to change now."

Another factor was how and where they put their children down to sleep at the resort. The McCanns' apartment was on a corner with easy access from the street. It is now considered likely that someone was keeping an eye on their comings and goings. And it wasn't until a whole year later, when finally they were given access to the police files, that Kate discovered that anyone checking the book at reception would have seen a note stating that the McCann party wished to eat in the tapas restaurant every night because they were leaving young children alone in the apartments and needed to be able to check on them easily.

The story of how Madeleine went missing need not be repeated here, but the book gives us what the press never could: a sense of the misery of that first night and those that followed. The slow breaking of dawn, followed by the sickening job of telling the news to relatives in the UK. Kate's inability to stop banging and bruising her fists on the metal railings of the veranda, "trying to expel the intolerable pain inside me". Gerry breaking down and "roaring like a bull".

The McCanns were soon, and wisely, given access to a trauma specialist, who immediately reassured the couple that they seemed like model parents. "I cannot overstate how much such kind reassurance meant to us at that moment," Kate writes. He explained to them the importance of taking control little by little, "starting with tiny actions as simple as making ourselves a cup of tea".

In fact, kindness and forgiveness - being gentle with yourself in the face of unrelenting shock - is the core, though perhaps unwitting, theme of Kate McCann's book. Her husband was able to shut off his pain for hours at a time in order to deal with the world - something that she admits she occasionally resented. With touching self-awareness, she describes how she could not do the same. She was unable to settle to anything that did not relate directly to finding Madeleine: "I could not even sit down unless it was for a purpose, to eat or to work at the computer."

She conjures a heartbreaking image of the bereft mother, condemned to pace up and down eternally, sniffing for her young. It was two years before she could listen to music or watch television, or allow herself to take pleasure in anything at all without feeling that she was letting her daughter down.

Hugging friends whom she hadn't seen since before Madeleine disappeared, she would find she could "hardly bear to let go", because she knew that the moment she stepped back and saw their faces, she would be reminded of "days spent together with Madeleine". She also says candidly that her sex life with Gerry suffered and that she finally took "a cognitive approach" to getting it back on track.

Years later, even beginning to feel more normal brings its own problems. She worries about what people will think if they see her speaking crossly to her other children in public. Or that, if "people saw me smile or laugh, they'd think it inappropriate". She has a fear that if anyone spots her shopping in Marks & Spencer, they will frown on her "for not going somewhere cheaper like Aldi and putting the pennies saved into Madeleine's fund".

If Kate McCann doesn't feel she deserves to be forgiven, it is striking nevertheless that this is a boldly empathetic and forgiving book. She writes without bitterness about the people whose correspondence goes straight into the "nutty box".

As doctors, she and Gerry have some professional experience of dealing with mental illness, and are not surprised that their tragedy attracts such attention - "within days of Madeleine's disappearance, several people with major psychiatric problems made their way over to Praia da Luz". And although the trauma specialist had warned them that they would lose some good friends (and they did), she is grateful for the "quiet majority". Astonishingly, perhaps, she still believes that "most human beings are inherently good".

Even though I am sure there is a readership for Madeleine, many others will feel free to discuss and comment on the book without having read it. I would urge them to be as kind and non-judgemental as Kate McCann has been. Although she and Gerry come across as remarkably strong - clearly their love for their two remaining children, together with the search for Madeleine, has kept them going - I don't think anyone should underestimate how vulnerable they are.

To endure tragedy of this sort, followed by relentless press attention, leaves you raw, your skin feeling stripped right off. One night almost a year after they lost Madeleine, the couple woke in the night in Leicester to find the whole room shaking. "With the occasional death threat turning up in our morning mail, it is perhaps not surprising that our first instinct was to think we were being attacked."

Thankfully the "attack" turned out to be an earth tremor. You hope for the McCanns' sake that, whether or not they ever discover what happened to their daughter, the agonising rawness - like the tremor - will eventually subside to nothing. l

Madeleine
Kate McCann
Bantam Press, 400pp, £20

Julie Myerson's next novel, "Then", will be published by Jonathan Cape in June. To read more reviews by her for the New Statesman, go to: newstatesman.com/writers/julie_myerson