M. Characters vs. Plot

What makes a great novel?  Is it the plot that doesn't let up and carries you through the book until you reach the end only wishing and praying that it will continue.  Or is it possibly the characters in the story its self?  Do you fall in love with the charaters to the point that when the author does something to them or causes them pain it causes you some sort of pain.  What does it for you?  Is it some of both and is there a balance that has to be in a book for you to keep from becoming too bored?