Stalin, to borrow Churchill's phrase, is "a riddle wrapped in a mystery inside an enigma". There are still heated arguments about how precisely we should judge the Georgian student priest who grew up to be one of the 20th century's most notorious mass-murderers. This owes much to the enormity of the crimes, as Claire Shaw says in this short but chilling book about the man and the political system that developed under his rule: Stalinism. (Very few political regimes have been personalised in such a way Nazism does not bear the name of Hitler, for example).

What visions underpinned his actions? What mechanisms enabled him to commit his crimes? Why did nobody stop him? Within Stalin's lifetime, Russia and her neighbours endured a series of violent revolutions, two world wars, the forced collectivisation of agriculture, a major industrialisation drive, and the violent cataclysms of the Purges. A vast social experiment was launched radically to remake the nature of human society on the basis of equality and the redistribution of wealth; its implementation resulted in a violent and coercive regime that had little respect for human life or the natural world.

But it is too easy to dismiss Stalin simply as a monster. Too easy and wrong. What is most chilling about Stalin, as this book shows, is that he was all too human.