JOHN JAKES, whose North and South (Dell) will soon be topping probably all the paperback best-seller lists (it's already at No. 1 on the Walden and Dalton charts), is better known to some readers not as a blockbuster historical novelist but as the creator of Brak the Barbarian. "It's an out-and-out Conan pastiche," says the engagingly forthright Jakes, speaking from his South Carolina home. "I've never tried to pretend otherwise." The Brak stories, originally published in pulp magazines, did have mass market paperback publication, he says, trying to remember ("I'm a bit hazy on this stuff--it was quite a while ago"). Jakes comes up with Avon, Warner and Dell as the houses who did them.

What makes the Brak saga intriguing is the fact that, in reality, it's not over. That is to say that Brak, struggling against sinister sorceresses and implacable ancient idols, spent what there is of the series (four books in all) trying to reach his ancestral homeland. It ended--or not quite--before he succeeded. Like Agatha Christie with her last Poirot and Miss Marple tucked away in a trunk, Jakes has a one- page outline finishing the adventures of his barbaric hero locked in a safe-deposit box. "Occasionally I'll get a letter from a fan," he allows, "wanting to know what happens to Brak." But the answer isn't forthcoming--yet.