Ships, Slaves and Sadists : SACRED HUNGER, <i> By Barry Unsworth (Doubleday: $25; 630 pp.)</i>

“Money is sacred, as everyone knows,” a character in Barry Unsworth’s rich and beautifully written ninth novel says with great irony. “So, then, must be the hunger for it and the means we use to obtain it.”

“Sacred Hunger” is set in the mid-18th Century, though the above remark, like many of the book’s moral lessons and debates, might also be applied to modern times. The plot, too--centering as it does on the purchase of slaves and their shipment from Africa to America--has important contemporary echoes. To Unsworth’s credit, though, he has not merely created a cardboard past and painted it with 20th-Century political correctness; he has given us a real, sweating, breathing, bleeding, complex world, a world in which blacks sell other blacks into slavery and whites flog and cheat each other to turn a profit, and a few heroic men and women of both races struggle toward justice against the prevailing social values and their own fears and doubts.

Unsworth’s pace is leisurely. The novel begins with a wealthy but debt-ridden Liverpool businessman named Kemp, who decides that the slave trade is the route out of his financial difficulties. Kemp commissions a ship to be built for this purpose, the Liverpool Merchant, and personally supervises the sail-making and woodworking, while his grown son Erasmus looks on.

From these very first pages, Unsworth displays his grasp of historical detail, and a talent for stitching one fine scene smoothly into the next. The proper sewing of sails, the fitting of oak planks tightly together to form the ship’s main deck, the notes of reluctant subservience in a workman’s voice--every thread is of the correct length, width and color. To man this slave ship, Unsworth mobilizes a cast of characters rivaling that of “Moby Dick”: a cruel, experienced captain named Thurso; a sensitive ship’s surgeon, Matthew Paris, who happens to be Kemp’s nephew, and a finely drawn group of seamen--fiddlers, drunks, sadists and simpletons.

As the Liverpool Merchant sets sail for Africa to take on its human cargo, Erasmus Kemp, home in England, sets a course he hopes will lead to marriage with a neighboring beauty named Sarah Wolpert. Though Unsworth shifts between these two story lines throughout the book, in the first half of the novel he wisely dwells on the scenes aboard ship. He has created such a convincing and intricate world there that the reader feels a small disappointment at each return to the more common domestic drama.

At sea, it does not take long for tension to develop between the pragmatic and merciless Captain Thurso and Kemp’s sensitive nephew, Matthew Paris. Thurso, like the Kemps, finds nothing objectionable in the buying and selling of human beings. His morality is the morality of the herd, a commercial religion based on a kind of despicable trickle-down theory. In one of his many ironic jabs at modern economics and mores, Unsworth describes the slave-trading era in England as “a time when the individual pursuit of wealth was regarded as inherently virtuous, on the grounds that it increased the wealth and well-being of the community. Indeed, this process of enrichment was generally referred to as ‘wealth-creation’ by the theorists of the day.”

A tyrant in a tyrannical time, Thurso mistreats not only the slaves, but his own seamen as well. The story is dotted with accounts of floggings, the application of thumbscrews, and other cruel punishments that serve to set some of the men against their captain. By the time the Liverpool Merchant is ready to leave the African coast with its valuable human cargo, the crew is stewing with resentment, sick with fever, hungry and thirsty. The ship reeks of excrement, is infested with rats; slaves and crew alike sicken and die, and, appropriately, the ship wallows for days in the hot African doldrums.

Meanwhile, back in England, the elder Kemp’s debts have multiplied, bringing him to his own appropriate punishment. His son Erasmus, whose narcissism Unsworth goes to somewhat excessive lengths to establish, sinks into temporary disgrace, losing, in the process, his beloved Sarah. At this point, roughly 400 pages into the novel, Unsworth leaves us to imagine the climax of the building tensions aboard the Liverpool Merchant, and leaps forward 12 years into Erasmus’ future and that of the ship’s crew.

This jump wounds “Sacred Hunger,” and though Unsworth’s talents are sufficient to retain our interest over the last 200 pages, the book never quite recovers its earlier pitch of dramatic intensity. The characters we cared so much about at sea return to work out a complicated morality play in another exquisitely drawn setting, but some readers may feel they have been pulled out of the theater moments before the film’s climax. Details of the moral battle between Thurso and Paris are provided in deft A very occasional but intrusive didactic voice also interrupts the smooth narrative flow: “It is when we make plans for an absence that we learn the extent to which we are needed at home.” “There are no stronger fetters than those we forge for ourselves.”

But this is a large and multifaceted work, almost Tolstoyan in moral and literary scope, and its beauties and strengths far outweigh these blemishes. Unsworth takes hold of the most central moral question--the causes of and responses to evil--and builds around it an entirely realistic world peopled by men and women--white, black and red--whom we care about until the last word.

In the course of this 600-page voyage, we are treated to numerous finely wrought scenes, any one of which is worth the tribulations of rough weather. We see sailors being shanghaied in English taverns, a ribald party in a private club, dinner in a sweltering colonial fortress, carpenters fitting the ship’s great timbers into place; there is a bit of humor and sex, intricate psychological portraits, philosophical debates on the nature of money and goodness and the proper role of government, historical asides, sea stories, antiquated healing procedures, and beautiful descriptions of jungle, sea and sky.

Most remarkably, perhaps, the author’s careful and striking accumulation of detail provides the feeling of complete realism, though the story takes place more than 200 years ago and the settings vary widely.

It requires a writer of consummate skill to pack all of the above into a serious novel while at the same time doing justice to the horrors of the slave trade. In “Sacred Hunger,” Unsworth has gone beyond that: He has shone a light into the swamps of human nature; exposed the muck of our materialism and the danger in confusing morality with marketplace values. The preeminence of those values--persisting in diluted form to this day--is what once allowed us to rationalize the selling of men and women.