" Interesting and insightful but deeply flawed in its concept and examination of the communist morale, ethics and philosophy. Not to say that from the purely historical viewpoint it's so unauthentic and primitive in exposing pre- and post- revolutionary history of the Russian communist movement that it's not even funny. Koestler surely knew something about it so it's quite a surprise for me that he chose to write on these topics in such a simplistic and inadequate manner - well, it's not a historical trait so some degree of fantasy and even mixing things a bit is, of course, tolerable but the book's extreme remoteness from the historicism is annoying for a person who knows some basics about those times. Maybe the author intended to combine some very interesting and deep reflections on historical materialism, pain and suffering (both physical and spiritual), betrayal and the contradiction between the duty and the sense of guilt and humaneness with such a vulgar simplifications and misrepresentations in order to make his novel (otherwise too abstruse, abstract and intellectually demanding for an average reader) more light-minded and easy-going or the obvious agitprop literature limitations (of which this book is a perfect example despite its depth and non-triviality) left their ugly traces but this creates a very mixed feeling.
More detailed review to follow (as I don't want to sound proofless). "
— Alexei, 2/19/2014