The Miracle Workers

Sixteen hundred years after his ancestors hid from galactic war on the out-of-the-way planet Pangborn, Lord Faide is finally uniting the planet under one rule. His. Aided by master jinxmen, his men are fearless, his demons terrible, and the hoodoo at his command unbeatable, as Lord Ballant soon finds out. However, the First Folk have waited for the opportune time to sweep mankind out of Pangborn's forests and into space or the grave. As his once victorious army is smothered by foam and stung by venomous insects, Lord Faile fights a long retreat back to his keep. With his jinxmen rendered powerless by the aliens' minds, all hope relies on Sam Salazar, a failed apprentice jinxman with a talent toward experimentation and empiricism.

As the Frisky Pagan pointed out, this is an almost identical story to The Last Castle. Both worlds are rocked by unthinkable revolts of once pacified people. In each, human society is saved only by the actions of an unorthodox youngster who embodies one of the virtues of modern man.
The proud and the arrogant suffer in both The Miracle Workers and The Last Castle, while the humble and the unorthodox are exalted.Vance keeps the story fresh, not only by crafting a new world, but by varying the perspective. The Last Castle followed the unorthodox Xanten as he seeks to learn how to save his people. The Miracle Workers instead tell the story of Lord Faide and his jinxmen as they watch (and hurl abuse at) Sam Salazar. This allows Vance to examine the situation from both the unorthodox and the orthodox views, and he extracts different lessons from each.

Honestly, this shrieks of message fic. The jinxmen are set up originally to be technical wizards, at least in the realm of telepathy and psychology. This mental technology has been honed to a mature, even a plateau, level. But their hoodoo reeks of superstition, and therefore must give way to the completely immature empiricism of Sam Salazar. The appeal of the nascent physical sciences compared to the mature parapsychology hoodoo of the jinxmen is overstated, with the latter abandoned way to easily by people who have had a lifetime of evidence that hoodoo works. But, hey, science is modern, and therefore better. Right? At least The Last Castle was clear that the social ills that had to be abandoned for humanity's survival were the same ills that caused the Meks' revolt. The Miracle Workers lacks that consistency of cause and effect. At least Vance follows Harlan Ellison's maxim that says that a story must entertain before it can educate. Personally, give me instead Edgar Rice Burroughs' idea that entertainment is the sole purpose of fiction.

That said, The Miracle Workers shines with more life than many of today's works, refuting the claim by many that the works of the past 15 years are more accessible than their predecessors.