Sword and Citadel - Gene Wolfe

If your mind hasn't been blown by the allusions, puzzles, relentlessly unpredictable plot and elegant language in the previous books, then prepare yourself. 

All the above elements reoccur in this fourth part, but blended by mastery.

Orwellian thought controlled races appear, there are horrifying war scenes, the mystery of the Claw is resolved (by dissipating in a deeper mystery), there's a storytelling contest that goes meta all over the four books, and the strangest conclusion to a sci fantasy saga I have ever read. All the fascinating background to what everything means is never stated. It occurs to you over the weeks after reading. 'It can't be!' is what you end up suddenly muttering to yourself after these books. You will be back.

Wolfe delivers again with his thrilling plot and philosophical riffs on time, idealism, loyalty, and the individual. Both epic and haunting.