The Oedipus Cycle is a trilogy of Ancient Greek tragedies by Sophocles. In Oedipus Rex, Oedipus tries to escape from a prophecy that he will kill his father and marry his mother. He kills a man (unknowingly his father) and marries the queen, his mother. In Oedipus at Colonus, Oedipus dies and his sons begin to fight. In Antigone, Oedipus' daughter, Antigone, is sentenced to death by Creon for burying her traitorous brother inside the city. Before Creon can rethink his decision, Antigone commits suicide.
The most popular website for book notes. SparkNotes was created by students for students, and their summaries are accessible and extremely well-written. Besides the usual plot overview, chapter summaries, and character analysis, SparkNotes differentiates itself with a section discussing themes, motifs, and symbols.
The original provider of professionally-written study guides, Cliffs Notes were available in print form before the Internet even existed. Their content is very comprehensive and includes an analysis of characters, detailed chapter by chapter summaries, critical essays, essay topics, and many other sections.
Their book summaries aren't as good as other providers, but PinkMonkey often has interesting insights that aren't mentioned elsewhere on the Internet. For example, they go over literary elements (like setting, conflict, and mood), compare and contrast, and symbolism/motifs. It's a good site if you want to find a unique fact or angle that other students don't know about.