is some overlap between the two works, there are also fundamental differences that overshadow them.
The works are alike in the following ways:
They are both marked by violence and betrayal. In some of these acts of violence, people do unspeakable things.
They are both defined by ambition.
They are both defined by family relationships, and by family relationships that are interwoven with power within an entire kingdom.
They are both defined by the unexpected and almost impossible happening at key moments near the end.
However…the themes vary greatly because the main characters vary greatly. The supernatural looms much larger in Macbeth, and the main characters in Macbeth (Macbeth and Lady Macbeth) are consumed by ambition. Ambition in the main characters in The Princess Bride is subsumed to other drives (skill, love, revenge), and the greatest of these, love, shines in Goldman's book as it never does in the play.