Macbeth is an interesting play. It has everything one could ask for: royal intrigue, betrayal, ambition, witches, and of course lots and lots of blood. I consider it Shakespearean a horror flick. You can look for the deep meaning, such as the psychological conditions various characters might be suffering from. However, it is rather hard to take the play seriously. It is actually fairly comedic.
Consider when Macbeth loses his mind:
The table's full.(55)
Here is a place reserved, sir.
Here, my good lord. What is't that moves your
Which of you have done this?(60) (Act 3, Scene 4, enotes etext pdf. 50)
This scene where Macbeth sees Banquo’s ghost always makes me laugh, and it is pretty easy to look at Act V as slapstick, with soldiers from both sides running back and forth. The fact that anyone would think moving trees meant the forest was really coming to get them is purely laughable. What was Shakespeare thinking?
Then there are the loose ends. My students ask what happened to Donalbain? He was the king’s other son that fled to Ireland and never returned. What happened to Fleance? Macbeth hired murderers to kill him and Banquo, but Fleance got away. Where did he go? What really happened to Lady Macbeth? She basically screams and dies offstage. Malcolm suggests that she violently took her own life.
Of this dead butcher and his fiend-like queen,
Who, as ’tis thought, by self and violent hands(80)
Took off her life (Act 5, Scene 7, enotes etext pdf p. 90)
It’s kind of a cop-out. Really, Malcolm is just quoting rumors. Also, how could Lady Macbeth go from being so cruel and bloodthirsty to completely losing it? She did not even directly kill anyone. She only handled the knives!
So while you can look at this as a story of guilt, betrayal and the costs of ambition, there is really not much in the way of substance here. Did Shakespeare mean for it to be taken seriously? It’s hard to say. He does seem to have been in a hurry when he wrote it!
I included a link to an essay on Macbeth, in which R. Moore explores the theme of guilt.
Through the experiences of Macbeth and Lady Macbeth, Shakespeare demonstrates that self-destructive guilt cannot be assuaged by recourse to action nor by even the most determined effort to expunge the pangs of conscience by active engagement in denial and transference. (paragraph 1)
So it is not impossible to find depth!
R. Moore. "Macbeth: The Theme of Guilt in Macbeth." enotes publishing, 2012