Shadow and Claw by Gene Wolf

The Shadow of the Torturer is the tale of young Severian, an apprentice in the Guild of Torturers on the world called Urth, exiled for committing the ultimate sin of his profession -- showing mercy toward his victim.

The Claw of the Conciliator continues the saga of Severian, banished from his home, as he undertakes a mythic quest to discover the awesome power of an ancient relic, and learn the truth about his hidden destiny.

The Book of the New Sun is unanimously acclaimed as Gene Wolfe's most remarkable work, hailed as "a masterpiece of science fantasy comparable in importance to the major works of Tolkien and Lewis" by Publishers Weekly, and "one of the most ambitious works of speculative fiction in the twentieth century" by The Magazine of Fantasy and Science Fiction. Shadow & Claw brings together the first two books of the tetralogy in one volume.