I believe, we need it. We are matured and grown enough for it.
The movies dialogue games soon begin to repeat themselves. This one has a much wider potential.
Since it is a novel, if the quote is not very individualized, make it longer, so we could recognize it. Two - three word quotes are not encouraged.
If the quote is not from direct speech, the one who answers must say from which part of the story it is and what it is about. If it is - who says it to (or about) whom and in which part of the story (If it isn't obvious, of course).
Choose quotes mercifully, games exist to give pleasure!

I'll start with an easy one:

"Hey, kid, they won't give you medals, they put you in the electric chair."

Sonny to Michael.
Q. "To them, that's Irish."

Michael to Tom, after the funeral.
Q. "I can see the top of it over your shirt, how about letting me see the rest of it?"

Assassin to Fabrizio.
Q. "Don't talk about it, please don't talk about it."

Lucy to Jules
Q. He felt her stiffen a little. "But not in the last six months."

Don't tell me it's difficult!
OK, I'll post new one:
Q. "Why do we have to pay him? What can he do to the three of us? We're stronger than him. We have guns."

Young Vito to young Clemenza and Tessio.
(Now that you added, "He felt her stiffen a little," the answer to "but not in the last six months" is Michael to Kay.)
Q. "They are clever enough to make a good living."

Vito to Clemenza about Bochiccios
Q. Mothers are like cops. They always believe the worst.

Michael to Kay.
Q. "Is it going to take that long?"

Nino to Jules
Q: I think maybe you'd better get a healthier fellow for this job.

Vito to Fredo re. Paulie.
Q. "You have my goods still?"

Clemenza to Vito

I saw their brains

(Not sure if that's exact. I don't have the book in front of me)

It's exact! Michael to Tessio.
Q. "What made Solozzo think he could get a deal with you?"

Michael to Sonny

Wait. I'll get you your money

Vito to workmen about furnace

"He sticks with me and he gets wiped out; he's figuring I can't win."

Michael to Tom re. Tessio's betrayal.
Q. "You f*****g bastard. I'll have you all in jail for a hundred years."

Woltz to Tom on the phone.
"We had a little argument and I straightened him out."

Moe Green to Michael

Do what I tell you, I'll make you rich.

Luca Brasi to Filomena.
"Hey, Ma, how about cooking me something to eat?"

Neri's nephew to his mother (Neri's sister)

"Oh, that" (italics mine).

Lucy to Jules, about that (Italics mine.)
"How come? I thought we were supposed to sit tight!"

Michael to Hagen, when informed by Tom that they had hit Bruno Tattaglia.

Your friend is in trouble, and his word don't go this far west anymore.

Billy Goff to Johnny Fontaine.
Q. "You're lucky I'm not your father."

Billy Goff to Johnny about Godfather

"The word is already out that he's to be brought here before he's allowed any of his old rights in the Family."

Turnbull, yours is Neri to Italian boy on the street.

Sonny to Michael, Tom, Clemenza, and Tessio re: Luca.

If I took a job like that, there couldn't be any strings attached.

Jules to Michael.
Q. "Have another drink if you like."

A: Vito to Tessio, Clemenza, & Tom after the Five Families sitdown

Q: You look like the devil himself.

Vito to Sonny.
Q. "You don't want to get involved with the police."

Michael to Enzo
"He wants to put a proposition to you. Can you meet him later on tonight?"