In Act III, scene 1 or "Macbeth", Macbeth invites Banquo to a banquet. What does this reveal about his character?

Macbeth is trying to appear normal.  He wants Banquo to feel comfortable and welcomed to the banquet.  By reminding him that he wants him to attend, it shows how cold and calculating Macbeth truly is.  He asks questions as to where he and Fleance are riding and when they'll return so he can set up the murder/ambush.  He says

"Here's our chief guest" referring to Banquo, and then reminding him before he departs, he says, "Fail not our feast."

This scene shows how far Macbeth has come in his evilness.  He is cold and calculating and is willing to have his best friend killed to ensure himself the throne.