There are 4 books in the Urth: Book of the New Sun series. The newest book is The Citadel of the Autarch which came out in 1983.

1
The Shadow of Torturer

The Shadow of Torturer
In a thoroughly decadent world of the future, Severian the torturer is cast out from the torturer's guild when he falls in love with one of his victims and allows her to die
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4
The Citadel of the Autarch

The Citadel of the Autarch
Severian the Torturer, possessor of the miracle-producing gem, the Claw of the Conciliator, experiences strange adventures as he journeys across the savage land of Urth