What I got from the book is this. MacBeth is a General in the King of Scotland's army and he wins many battles and the king likes this so MacBeth gets more power because of it. Then, for no reason at all, MacBeth comes across a trio of witches in the forest with his lackey. The witches predict that MacBeth will be king and he believes them. He then thinks of a way to assassinate King Duncan. He's chicken and a loser so he convinces his wife to kill the king by seducing him and then killing him with a dagger. That's as far as I got. I find it pretty boring. MacBeth's a gullible pansy who has his wife do all the work. I also agree with Purplicious when she said that the prophecy would go unnoticed and MacBeth would never have become king if he didn't hear it himself. I believe he's a power hungry prick that loves fortune above everything else and the prophecy was just an excuse to do what he was planning.
I'll say again that I read it really fast and didn't absorb all the material. There were some good lines, but I don't have the book on me so I won't post them.