First of all, it's dramatic tragedy and myth, not fiction.  Sophocles actually makes it fairly modern in Classical Greek terms by limiting the role of the Chorus and the gods in the realm of Oedipus' choices.  The play is very humanistic, much like Shakespeare's tragedies, which were written long after, in the Renaissance.

Nevertheless, Sophocles' Oedipus Rex represents the ancient Greek tragic tradition by its use of the following:

• Myth as a basis for commenting on the role of fate and free will in human affairs
• The Greek Chorus and its function as the ideal audience, as an intermediary between the actors and the audience, and as a choral form of praise
• Its humanistic, tragic, and thematic focus on knowledge, fate vs. free will, death and suffering.  It delivers the message that hubris leads to tragic mistakes which, in turn, lead to suffering and death.
• Its ability to mirror human predicaments, arranging its plot, by the end, to purge its audience of pity and fear