The value of the humble kip

We live in self-conscious times. So maybe it's not surprising that we don't care very much about the seven or eight hours we pass every night in a state of unconsciousness. In other words, asleep. Biologist and science writer Paul Martin's mission in this energetic and immensely readable book is to raise the status of the humble kip. In the light of the Selby rail crash (which would almost certainly not have happened if driver Gary Hart had not been up half the night chatting to a woman friend), this book comes as a timely reminder that we ignore sleep at our peril. Indeed, as Martin points out, more car accidents happen as a result of the driver falling asleep at the wheel than for any other reason.

Every year we happily load our kids into the backs of our cars and set off on the great British holiday driveathon to southern Europe, conveniently ignoring all the evidence suggesting that we might be endangering our loved ones as well as ourselves. On average, we sleep an hour and a half less every night than our forebears a century ago. We're chronically sleep-deprived. In fact, not getting enough sleep has become a kind of badge of urban cool, a sign that your social life has the edge over your snoozing. So our lives are longer and more sleepless, but, says Martin, are they any more satisfying for that?

This is as good a popular science book as I have read, which is to say it treads lightly but comprehensively across a relatively complex subject (sleep is, admittedly, not as complex as quantum physics, but it has its moments) without shirking its responsibility to explain and illuminate.

Counting Sheep doesn't say anything scientifically new about sleep (though there will be plenty that's new to the average reader). What it does do is cast light on the scientific state of play so far. Counting Sheep will tell you why sleep-deprived people are shorter, why some blind people dream in pictures and others don't, and what dreams are actually for. Martin's achievement is to do this with such vivacity and infectious enthusiasm that by the end of this book you'll be racing for your bed to try out a few sleepy experiments for yourself.

As Martin notes, sleep doesn't just help us get through the day. Nor is it merely an absence of consciousness. During Rapid Eye Movement sleep, when most, but not all, of our dreaming is done, our brains are more active than they are during wakefulness. Sleep, it seems, is absolutely vital to our ability to process our experiences and emotions. So important is it, that nature provides ingenious biological solutions for animals which would otherwise find sleep impossibly dangerous. Dolphins must surface every few minutes to breathe, so the two halves of their brains take it in turns to sleep, each for an hour or so at a time before the other half takes over.

Birds, too, can sleep with half their brains awake and the corresponding eye open and watchful.

Experiments on lab rats and dogs have shown that animals deprived of sleep for a few days simply lie down and die. Yet still, with foolish hubris, we humans try to cheat it.

Impressive in the range and depth of its research, Counting Sheep also tackles some of the most pertinent philosophical questions raised by science's understanding of what sleep is. Do the twilight zones between sleep and wakefulness constitute a third state of being, somewhere between consciousness and unconsciousness? Will intelligent machines need to sleep? And is someone who commits a crime while asleep properly responsible for their actions?

As a former insomniac, I've read countless books on sleep, usually while struggling to achieve same, but rarely have I encountered one as sure-footed and hospitable as this.

Silvertown: An East End Family Memoir by Melanie McGrath is published by 4th Estate at £16.99.