How is the theme of happiness depicted in the novel Fahrenheit 451?

In Fahrenheit 451 the concept of happiness is an elusive one since the society has been desensitized to any genuine emotion.

There is little family interaction that can produce true emotion. 

People whiz through their shallow lives just as they drive at high speeds, experiencing no genuine feeling. During his visit to Montag, Beatty tells him, 

"Life becomes one big pratfall, Montag; everything bang, boff, and wow!" 

This disconnect is what Clarisse questions when she...

In Fahrenheit 451 the concept of happiness is an elusive one since the society has been desensitized to any genuine emotion.

There is little family interaction that can produce true emotion. 

People whiz through their shallow lives just as they drive at high speeds, experiencing no genuine feeling. During his visit to Montag, Beatty tells him, 

"Life becomes one big pratfall, Montag; everything bang, boff, and wow!" 

This disconnect is what Clarisse questions when she converses with Montag in the exposition of the novel. She laughs when he asks her what she and her family talk about, because it is so unnatural to her that he would not know what to say to his own family members. Then, she turns to him and pointedly asks, "Are you happy?" Montag's reaction is very telling: "Am I what?"

Clearly, Montag does not know the meaning of the word, but he has enough depth in himself that he begins to wonder about what Clarisse has said.

He was not happy.... He wore his happiness like a mask and the girl had run off across the lawn with the mask and there was no way of going...to ask for it back.

When he returns home and finds his wife nearly dead, Montag begins to seriously question his existential state the next day. He wonders what is in books that a woman would be willing to die for them. Perhaps there is some emotional contentment that comes from reading, he thinks. It is then that Montag looks at the books he kept from the fire, books which are the record of true human experience. This genuine experience is one that Montag then searches for as he contacts Faber and later becomes a part of the community that knows the meaning of happiness.