Many stories are only understandable and fully appreciated when placed in the context of a society, setting and time. Just as the invented phrase 'grang-grang' makes sense only after an explanation, so does the "culture codes' or 'historical codes' (Barthes) introduced by a writer become understandable when the context is known.
The clue towards cracking these codes lies in knowing the author.
"..the author is defined as a certain field of conceptual or theoretical coherence..."
"..the author is a definite historical figure in which a sense of events converge.."