The book goes into a much longer explanation of it, but the final scene conveys the message perfectly: Kay knows, despite what Michael had just told her, that in fact, the answer was "yes."


I always have fun with friends posing this "what-if" scenario about the ending:

MICHAEL: This one time, I'll let you ask me about my business.
KAY: Is it true?
MICHAEL: (long pause)
You ask me if it's true? All right, I'll tell you: Yes, it's true. You're damn right it's true. Carlo set up my brother to be killed and he beat my sister within inches of her life at least twice that we know of. He sold Pop out, he sold Sonny out, and he was gonna sell me out the first chance he got. You're looking at me like I'm a monster, and let me tell you: I am. I'm a monster to anybody who goes against my blood. Anybody who threatens you, or me, or our children, is gonna find out the same thing. And someday, you're gonna be thankful for it.