When Captain Beatty comes to visit Montag at his home, he gives the entire history of how their society became the way that it was. He described how people became the embodiment of "ignorance is bliss". Novels took too long to read, so they were shortened and shortened, and finally people just stopped reading them. Schools started eliminating philosophy or any other classes that encouraged deep thought. Instead, they taught things that filled the students heads with useless information and made them feel like they were smart and intelligent, but completely discouraged any real ability to analyze or think through things for themselves. Their society's entire motto is "ignorance is bliss"; they feel that if they don't know about it, they can keep being happy. Unfortunately, it doesn't really work. Hence, Millie's suicide attempt. They spend so much time staying busy so that they don't have to think about how miserable they really are. It is an empty promise; they've been surrounded by messages that inidcate misery is bliss, but it really isn't.
For their society, knowledge comes in the form of books, which are banned. But look at the people who have read, and who are different. They seem to have a strange power over unhappiness. Clarisse and her entire family are unusually happy, and Montag immediately notices the difference. He craves the quiet power that she has. When Beatty tells him about books, he craves the power that he can sense in them, which will help him to make sense of his life, and to find true happiness. He craves the inner peace that he senses in Faber, who has read and has knowledge from books. And then once Faber finds Granger and the other people who have knowledge of books, he feels empowered for the first time, hope for the first time, and the actual tools needed to make a difference in the world. For Montag, knowledge is power.
I hope that helps! Good luck!