Just as the Confederate cause seems doomed, deliverance arrives in the form of 20th-century weapons. History and science fiction merge in this latest from Turtledove (A Different Flesh, 1988; Agent of Byzantium, 1987 )--something that the publisher calls ``speculative fiction.'' It's not bad. What if the South had been armed with modern repeating rifles? South African white supremacists with access to a time-travel machine conclude that their own loathsome policies would find sympathy in an independent Dixie and, accordingly, begin historic, large trans-shipments of the sturdy, reliable AK-47 rifle from 21st-century Johannesburg to 19th-century Virginia. Dazzled and delighted by the possibilities of the weapon, Robert E. Lee and his troops grab the guns and turn the war and American history around. Acting on uncanny tips from the Afrikaners, Lee reverses the Battle of the Wilderness and within months the rebels seize Washington, D.C. A new nation is born, just the way the Boers hoped it would be. Or is it? The Confederate States do indeed continue to allow slavery, but the realities of world opinion and economics quickly influence new national policy. General Lee succeeds Jefferson Davis as president and brings his sober ethos to southern government. The South Africans, who have dug into their own company town in North Carolina, are outraged by the perversion of what should have been an eden of apartheid, and they bring new weapons to bear on their former darlings. But they have not reckoned on southern orneriness. It is a fatal miscalculation. Readers willing to wink at the time travel will find a well-researched and well-written account of a nation that didn't happen. Literate rebs will read it again and again and again.