But Michael "lurved" Kay. He convinced her to take those night time college classes. And Michael got over Appolonia quickly because it was nothing a few megavitamins couldn't cure.
Nice Annie Hall reference there....

Anyway, the obvious comparison of Michael's wives is such a crucial element of the story. Of course Appolonia would've made a better 'Mafia' wife (I love the passage in the novel describing her first weeks/months of married life). But the initial relationship and eventual marriage to Kay is needed to emphasize the transition between the once rebellous Michael who wanted nothing to do with his father's 'Business'...and the hardened Don we came to know & love.
While we are not supposed to be nuts about Annie-er, I mean Kay, she is really the conscience of the story...
Apple