A Million Open Doors — John Barnes

Nou Occitan is a place where duels are fought with equal passion over insults and artistic views alike. Giraut--swordsman, troubador, lover--is a creature of this swashbuckling world, the most isolated of humanity's Thousand Cultures.

But the winds of change have come to Nou Occitan. As the invention of the "springer"--instantaneous interstellar travel, at a price--spreads throughout the human galaxy, the stability and purity of no world, no matter how isolated, is safe. Nor can Giraut's life remain untouched. To his wonder, he is about to find himself made an ambassador to a different human world, a place strange beyond his wildest imaginings.