This novel/play is a thinly disguised criticism of communism, but on another level, it describes the tendency of all Western governments (including capitalism) to deal with abstractions and generalizations rather than individual lives.  The telling line is "Death is no mystery to us.  It is the natural conclusion to political diversity."  Koestler was very concerned with the dilemmas of the people under Franco's rule in Spain, and like Hemingway, wrote as his contribution to the world-wide anger and revulsion at the civilian casualties involved in the civil war.  This period saw as well the Guernica mural by Picasso.  So Koestler drew from the political tensions of his time, as did many of the world artists of the 1930s.