'The Family That Couldn't Sleep' of this book's title are Venetian aristocrats cursed by the genetic disease Fatal Familial Insomnia. For the past 200 years, in generation after generation, it has struck, apparently at random, damaging the sleep centre (the thalamus) in the brain. The victims, deprived of the restorative powers of sleep, finally succumb over several tortured months from physical exhaustion. So far, so obscure, but the ramifications of this bizarre illness turn out to be quite fascinating, taking in both the health hazards of cannibalism, and those of mad cow disease, while at the same time illuminating a pivotal unanswered question of contemporary medical science.

The common link is that Fatal Familial Insomnia and mad cow disease are both caused by that most profound biological anomaly of the last hundred years, prions – non-living proteins from which all cells and tissues are made that nonetheless have the ability to change and destroy other proteins just