The Big Necessity, By Rose George

When I returned from a visit to Zurich in 1992, I bored everyone to death talking about the toilet in one particular restaurant. Pressing what I thought was the flush button produced a different result altogether: suddenly, there was a buzzing noise and the toilet seat gyrated 180 degrees, so that the part I'd been sitting on was now at the back and the "untouched" part at the front, ready for the next visitor. So I'm afraid I can well understand Rose George's urge to write an entire book about the extraordinary toilet habits of the world's population, subtitled "Adventures in the world of human waste".

Her book has a political purpose too, though. 2.6 billion people in the world have no sanitation – and that means nothing at all, not even a filthy outhouse or a public latrine.

In 2007, readers of the British Medical Journal were asked what they thought was the biggest medical milestone of the past 200 years and they voted for sanitation. In Japan, the past 60 years have seen a revolution in toilet design so that, while the British and Americans are happy enough with basic functionality, the Japanese have a choice of heated toilet seats, bidets built within the toilet, and hot-air blasts to dry them instead of toilet paper. The contrast with parts of India, for example, or South Africa, couldn't be greater, where women run the risk of being raped because they have to defecate out in the woods late at night, and their children continue to die of cholera and dysentery.

This an extraordinary study in part because it focuses on an issue which we rarely discuss, or even give much thought to. George puts that down to one-part embarrassment and one-part taking our comforts for granted. Flushing loos aren't a luxury – they're a basic human right.