The two love separate lives and the society has set it up so that relationships are shallow, superficial, and virtually meaningless. This society is all about giving people the illusionsof what they desire with none of the heartache. Montag realizes painfully so that he is not in love with Mildred and has never been in love with her, nor she toward him. He realizes that they are just cohabiting and have been. He, through his experiences with Faber and Clarisse, sees through the illusions and wants more. Mildred is constantly engrossed in her TV walls and ear-shell radio. The two rarely interact. They do not share a bed like married bed and they certainly do not share any real feelings or emotions between them. They live mediocre lives somewhere in the middle, never truly happy, but also never sad (almost never, there are several suicide attempts in this society for those who become unoccupied long enough to realize there is little if anything to live for).
They have a difference of opinion about information and the way they should live their lives. She is a willing participant in the new government and the mindless lifestyle of the television screens. Although it is clear she is miserable, she pretends to be happy and enjoying her life. She is a natural follower..one who never questions or investigates on her own. She likes being told what to do, and she probably has never read a book willingly on her own to learn things for herself. These people are easy to control.
Montag, on the other hand, refuses to do this. His eyes are opened to what used to be through his neighbor, Claire. Her family speaks of what life was like before when firemen put out fires and saved lives and property. Montag feels sick when Claire disappears and also when he burns the books. His clear turning point is when the woman refuses to leave the home she has lived in for so long and she, along with her books, goes up in flames. He saves books and dares to read them in front of his wife and her friends. He makes friends with former professors and lovers of knowledge. Montag is a questioner. He wants to know the "how" and the "why"...not just the "what" and the "who". He thinks for himself.
This difference in opinion is a huge factor in the rift that has developed between Montag and his wife.