Gene Wolfe's The Book of the New Sun is an extraordinary epic set a million years in the future, on an Earth transformed in mysterious and wondrous ways, in a time when our present culture is no longer even a memory.
Severian, the central character, is a torturer exiled from his guild after falling in love with one of his victims, and journeys to the distant city of Thrax, armed with his ancient executioner's sword, Terminus Est.