This is as good a place as any to mention that Koestler's long-lost original German manuscript titled "Sonnenfinsternis" was discovered in 2015 by a doctoral student digging through the archives of Zurich library. "Darkness at Noon" as known until then was a hastily completed translation into the English by Koestler's lover Daphne Hardy, available German versions being, in turn, back-translations from the English.
Both the German original and a new English translation have since been published.
Both the German original and a new English translation have since been published.
https://news.ycombinator.com/item?id=18188912 (HN 2018)
https://en.wikipedia.org/wiki/Darkness_at_Noon