Reviewed by George Rosie

Anyone who thinks present-day capitalism is brutal should consider the story of the Liverpool slave ship Zong. In the summer of 1781, while the Zong was making her way across the Atlantic with a cargo of 470 African slaves, a fever broke out that killed 60 of the slaves and seven crew.

At which point the skipper, one Luke Collingwood, made a businessman's calculation: if the slaves died of disease the loss would be incurred by the ship's owners; if they were thrown overboard into the sea, the loss would fall on the insurance underwriters.

To Collingwood, it was a no-brainer. Over the course of three days, 122 sickly-looking men and women were pitched over the side to drown or be torn apart by sharks. Another 10 slaves, driven mad by the treatment of their fellows, jumped over the side to their deaths.

When the Zong docked in Jamaica, Luke Collingwood said the killings had been forced on him by lack of drinking water - yet he still had more than 400 gallons on board.

But when the Liverpool businessmen who owned the Zong and its cargo claimed their insurance money, the insurers refused to stump up. This forced the slave traders into an expensive legal action which, after months of tortuous argument, they lost. The surrounding publicity - which brought home to (some of) the British public the awfulness of the business - helped the abolition movement. The slave trade (but not slavery) finally ended in 1807.

The voyage of the Zong is one of many horrors in The Slave Ship by American historian Marcus Rediker. By concentrating his prodigious efforts on the so-called Middle Passage - the transatlantic journey from West Africa to the Caribbean and North America - Rediker has added a wealth of detail to the huge literature on the trade which probably killed as many innocents as the Holocaust.

The story of the transatlantic slave trade is one of countless victims, precious few heroes and no end of villains. It was a conspiracy of evil put together by devout Muslims and pious Christians. According to Rediker most of the chieftains who delivered their fellow Africans to the slave ships were followers of Muhammad, while most of the skippers, slave merchants and plantation owners were respectable members of the Church of England. One slave-ship skipper - John Newton - went on to become a Church of England vicar and pen the words to Amazing Grace.

Rediker's description of the typical British slave ship is vivid. He describes it as "a strange and potent combination of war machine, mobile prison and factory. Loaded with cannon and possessed of extraordinary destructive power The slave ship also contained a war within, as the crew (now prison guards) battled slaves (prisoners), the one training its guns on the other, who plotted escape and insurrection."

The slaves lay packed below decks, without room to stand up, usually in their own filth and with hardly enough air to breathe. The rebellious were manacled. Women and children were separated from men to avoid "immorality". Food, water and exercise were given sparingly.

Around 12.5 million African slaves crossed the Atlantic. It is estimated that 1.8 million of them died en route.

Rediker has produced a gripping study of one aspect of a great evil. He has researched widely and deeply. But it's not a volume to be enjoyed. As he writes in his introduction: "This has been a painful book to write, and if I have done any justice to the subject, it will be a painful book to read. There is no way around this, nor should there be."