IT was a special pleasure to see things eaten, to see things blackened and changed. . . Montag grinned the fierce grin of all men singed and driven back by flame.
In terms of character progression, the opening paragraph is key to introducing and understanding Montag. He is a fireman, and in Bradbury's future, firemen don't put out fires. Firemen start them, and most often target books to be burned. Montag loves his job. He loves burning things. He loves burning books. He doesn't question what he is doing. That's important because it highlights just how much Montag changes throughout the story.
"You weren't there, you didn't see," he said. "There must be something in books, things we can't imagine, to make a woman stay in a burning house; there must be something there. You don't stay for nothing."
This quote shows Montag's belief system beginning to crumble. He doesn't understand why the woman would stay with her books, but he does begin to question whether or not books might hold some value beyond fire fuel.
"And I thought about books. And for the first time I realized that a man was behind each one of the books. A man had to think them up. A man had to take a long time to put them down on paper. And I'd never even thought that thought before."
The quote shows the continuing debate Montag is having with himself about the value of books. For the first time ever, he considers that a person spent a lot of time constructing that book. Montag is beginning to realize that what he does by burning books is undoing all of the hard work that went into writing the book.