The universe hangs in balance between chaos and order. Magic is chaos; rationality and logic are order. One man's task is to bring order and eliminate chaos. He is the traveler in black.
The traveler brings order by giving people what they wish for. But he gives in a poetic sense. Those who are blessed by the traveler get exactly what they ask for, but not what they want. For example:
"By your favor, sir," said a boy of ten or twelve years, hunting a hedgerow near the village Wyve, "are such plants poisonous or wholesome?"
Offering for inspection a glabrous brownish fungus.
"Wholesome," said the traveler. "They may be fried."
With a moue, the boy tossed the toadstool aside.
"Are you not glad to have found that it's edible?" asked the traveler. "I took it you were gathering food."
"No, sir," said the boy. His voice and eyes were older than his years. "I seek poisons to give to my mother; she rules me unkindly and will not let me do whatever I like."
He sighed enormously. "Ah, that I might recognize instanter what may be relied upon to entrain death!"
"As you wish, so be it," said the traveler, and went on, leaving the boy weeping because he realized: no matter what diet is chosen, sooner or later death ensues.
The book consists of four separate stories. The prose is unlike any other Brunner book I've encountered. It sounds like Jack Vance. The stories are not compelling. The prose is interesting, but not sufficiently so. Give this a pass.