The Mount by Carol Emshwiller, Small Beer Press, 2002, $16.00

The ancient Roman festival of Saturnalia marked the end of the autumn planting season and the start of the winter season of idleness. It was a time of relaxation and renewal. Many customary restrictions were suspended, distinctions of social class were largely ignored, and traditional roles were ritually reversed. Masters served their slaves at mealtimes in Roman households, and each home elected a Saturnalicius Princeps – "Master of the Saturnalia" – who got to order everyone else around for the duration of the festival.

This social inversion was limited, of course – you wouldn't find slaves having their masters whipped – but spending some time in their servants' shoes must have done something to enhance the empathy of masters for their slaves. At least some slave owners must have been influenced by the annual tradition of switching places – perhaps reflecting upon the arbitrary nature of fate and men's relative positions in the world.

We don't have a Saturnalia to turn the world upside down around us once a year. For our periodic taste of social inversion, we have to turn to sf and fantasy, where it has been a recurring theme since the utopian fantasies of the 16th century. Inversion has been one of sf's sharpest tools of social criticism, whether it's handled satirically (as in Pierre Boulle's original Planet of the Apes) or in deadly earnest (as in Suzy McKee Charnas's Holdfast novels). Sf inversions snap us out of our comfortable assumptions and force us to ponder the deep contingency of our social and cultural patterns.

Stephen Barnes's ambitious new novel Lion's Blood takes the Saturnalian reversal of masters and slaves and makes it stick. He presents an American South settled by black African explorers whose descendants use white slaves to work their plantations. The story centers on Aidan O'Dere, a young Irishman abducted with his mother and sister by Norse slavers. Sold into servitude on the estate of the Wakil Abu Ali Jallaleddin ibn Rashid al Kushi in New Djibouti, Aidan is befriended by Kai, the junior son of the Wakil. As young men Aidan and Kai enjoy a carefree relationship in which the central fact of their unequal status can usually be overlooked. But as they grow older the inequities of their positions forces them apart. Kai struggles to accept the constraints of his adult role, and Aidan chafes under the yoke, seething as his mother dies in bondage and his wife and infant son are taken to serve in another household.

Switching the roles of black and white in the Old South is an audacious and at the same time seemingly obvious idea – so much so that it's strange to realize it hasn't been tackled in quite this way or at such a scale before. Sf has reversed the roles of animals and humans, and women and men, dozens or even hundreds of times, and the annals of alternate history are just about defined by tales in which the historical vanquished become the victors; but issues of race relations have largely been handled – when at all – allegorically, with aliens taking on the role of the oppressed, as in the film and television series Alien Nation.

Surprisingly, the most direct sf confrontations with racial issues date back to the 1950s, 1930s, even the 1910s. T. Shirby Hodge's novel The White Man's Burden (1915) imagined a utopian civilization thriving in Africa in the year 5000 A.D., while the warlike, backward whites remain confined to North America. In The Long Way Back by Margot Bennett (1954), explorers from an advanced African society travel to a post-holocaust Great Britain, where they find the remnant whites living in caves. But as the civil rights movement heated up on the political stage, explicit treatments of racial subjects became rare in sf (even as non-genre writers took bolder steps). Octavia Butler gave us sf's most direct grappling with American slavery with Kindred (1979), wherein a 20th-century black woman is transported to the 19th-century South and becomes a plantation slave, but that was perhaps the only major example of the latter half of the 20th century.

There's no space here to investigate the complex cultural dynamics that left the genre unwilling to tackle racial matters during that period, while many other controversial social issues, from environmentalism to feminism, found a welcoming pulpit in sf. But perhaps the subject has waited for the advent of more African-American writers in sf. Feminism wouldn't have become such a strong part of sf in the 1960s and 1970s if more female writers hadn't taken up their pens – and even today the politics of so-called "authenticity" bring criticism upon a male writer who takes up a serious feminist theme. It's hard to imagine a white writer being encouraged to develop a story like Barnes's, and in earlier years there were precious few black sf writers who might have taken it on. Recently, though, we've seen a flowering of African-American talent in the sf world, with the rise of Nalo Hopkinson, Tananarive Due (who is Barnes's wife), Sheree Thomas, Barnes, and others, so Lion's Blood may be the first ripple of a coming wave.

Despite the obviousness of the role reversal, the scenario of Lion's Blood packs a significant amount of power. Images of the horrors of slavery have become so commonplace since the days of Roots that one might expect they've lost some of their provocative potency, but there are subjects whose moral outrageousness permit them to survive nearly any level of familiarity. The Nazi slaughter of the Jews is one such, and the enslavement of blacks in America is another. And so when we see the quiet life of the O'Dere crannog shattered by the attack of the slavers, and watch as families are broken up and spirits crushed, and when we witness the cruelty and filth of the slave ships that make the Atlantic crossing, we cannot help but be moved, though Barnes shows us nothing we didn't already know. Nevertheless, the familiarity of these horrors takes some of the edge off, because Barnes doesn't reinvigorate any of these wrenching moments with anything of his own – it's like he's following a script, and his characters are merely actors in a dramatization. Lion's Blood engages our compassion, empathy, pity and anger, but it buys them cheap, and with borrowed coin.

Barnes might well have made Lion's Blood into a revenge fantasy, taking the opportunity in a spirit of interracial fury to visit upon whites the miseries endured by blacks. Or he might have taken the chance to indulge in a bit of inverse racism, and given us an African-derived civilization more humane and enlightened than the European. But instead – to his credit – he has chosen to champion a doctrine of human universality in which the full range of human nobility and frailty can be found in any group and any culture. Barnes plays his inversion with impeccable fairness, and his willingness to portray his black masters in as cruel a light as their real-world white counterparts lends an extra weight to the mistreatment and dehumanization he depicts.

Unfortunately, what involvement Barnes's novel generates comes from the undeniable emotional force inherent in its premise, not from the characters or their story itself. As a literary experience, Lion's Blood is too often bland and clumsy. Barnes tells when he should show, and his descriptions fail to generate vivid images, employing vague gesture or hyperbole in place of concrete detail. The crannog's fishermen return to the village "sharing a jest here, a barbed comment there." Better to let us hear that banter. The Wakil's slave cook "magically" fashions flour into "the world's tastiest confections," but this gives us nothing we can see, smell, or taste. The Wakil's warrior brother, Malik, practices his art with precision, "every motion spontaneous, reflexive and yet calculated for maximum effect." We may understand from this that Malik is an excellent fighter, but we can't see it – there's not a single image around which we can begin to envision the scene.

The weakness of description contributes to the most disappointing aspect of Lion's Blood: the depiction of the world that results from Barnes's alternate history. Without more tangible detail, we don't get to experience this African America enough – it doesn't come alive as a fully imagined world. And the alternate history, as it's outlined in the text and in Barnes's brief afterword, isn't particularly well conceived. The dominance of Islamic culture seems a peculiar choice. Why not give us a civilization derived from native African roots? After all, Islam is as much a legacy of servitude for blacks as Christianity, brought by Arab slavers, not grown in African soil. And it seems unlikely that Islam and Christianity would even have appeared in Barnes's altered timeline, which has the Roman Empire snuffed in the cradle by Egypt and Carthage. Even if we grant this much parallelism, it's just about impossible to believe that a musical genius named Mozart would arise in this vastly changed Europe, or that a painter called da Vinci would sketch something recognizable to us as The Last Supper. The Ethiopian city of Addis Ababa was founded in our world in 1892, so how could it become the capital of the African empire in Lion's Blood? These might be minor quibbles if Lion's Blood offered a wealth of other, more convincing detail, but it doesn't.

What Lion's Blood does provide is a welcome opportunity to confront again a despicable chapter in American history, and to view it from a new perspective – which is always useful in helping us prevent familiarity from breeding indifference. Barnes brings to the subject a remarkable generosity of spirit, as he resists the path of anger and retribution to offer instead a broader meditation on the cruelties humans visit upon each other. It would have been so much more meaningful if he could have matched his moral vision with an artistic one of equal caliber.

Carol Emshwiller's new novel tackles similar themes from a somewhat different perspective. The Mount puts human beings in the role of horses, bred and kept and ridden by the alien Hoots, who have conquered Earth sometime in the not-too-distant future.

The Hoots are smallish, with large heads, vestigial legs, and powerful hands. They ride on human shoulders like toddlers, unable to support their own weight for long on their weak limbs. Men they call Sams, women Sues. They breed some for size, and others for speed. They race their humans and show the prettier ones and they admire human strength and grace. Hoot children play with doll humans, and the walls of Hoot homes feature portraits of famous human steeds.

It's a scenario that might sound impossible to keep from descending into absurdity, but – as she has done in other novels and stories such as Carmen Dog and "Mrs. Jones" – Emshwiller balances delicately on the beam, carrying the tale straight-faced with a combination of precise language, gentle humor, a near-perfectly pitched voice, and a tenderness toward her characters that draws us in and beguiles us. We're too involved in her story to wonder churlishly if the premise might be too ridiculous.

Like Barnes, Emshwiller centers her story on the relationship between a young master and his equally young servant. The mount of the title is Charley (are we meant to read "Charley Horse"?), called Smiley by the Hoots, who has been chosen to host the heir to the Hoot throne known as The-Future-Ruler-of-Us-All. Charley calls him Little Master. They train together and they play together, rider and mount learning each other's ways. Alone in his stall, Charley dreams of whisking his Little Master away from the overseers, whom Charley thinks treat The-Future-Ruler too harshly. When a band of wild humans led by Charley's father overruns the Hoot town, Charley saves his Little Master's life from the mob, and carries him off to the humans' rough village.

Emshwiller delves deeper into the psychology of servitude than Barnes by giving us a central character raised in slavery who accepts it as his natural condition. Charley resents his "rescue" by his father. He misses the comforts of life with the Hoots: "I like our old stalls with hot-and-cold running water and fancy kitchens, heaters you can turn on anytime you want." He has absorbed the viewpoint of the Hoots so thoroughly that even the sight of unmounted humans in the village makes him uncomfortable. "I just can't get used to seeing all of us Sams and Sues walking around with no Hoots on them. They look like half-people." Charley believes in the structure of Hoot society – the freedom offered by his father looks like another, worse sort of servitude, more work and fewer benefits.

Emshwiller gets to the heart of what keeps slaves in their place – what keeps all oppressive hierarchies running, despite what might seem obvious inequities to an outside observer: the dynamic of oppressor and oppressed, the inertia of established culture, the seduction of propaganda. "How can you be even a little bit civilized," Charley wonders rhetorically, "without Sams and Sues keeping at their jobs like they're supposed to?" Resistance means hardship and suffering, the upheaval of the social order, and few even among the downtrodden will choose that path when it's so much easier to stay in a comfortable stall.

As Kim Stanley Robinson observes in his blurb for The Mount, we are all mounts – we're all caught up in one way or another in systems like Hoot servitude, kept in our places by fear, or a love of ease, or inertia, or sheer laziness. Emshwiller reminds us of this, shows us how it happens, and how very difficult it can be to escape.