Bud has idolized his father since the beginning of the novel. He carries around a newspaper clipping of Herman, convinced that he is Bud's father. Herman almost has this sense of celebrity about him, unreachable and untouchable. Bud has a perfect image in his head about what Herman would be like, what he would say to Bud, and what Bud would say to him.
When Bud finally meets Herman, his dream of what his father would be like comes crashing down around him. He ran away, traveled far, and had many hardships on his way to meet Herman, and when he reaches Herman, Herman is not who Bud thought he would be. Herman is aloof, abrasive, and sometimes unkind, as he tries to push Bud away.
By the end of the novel, Bud realizes that Herman is a flesh and blood man, not like the untouchable dream dad Bud had in his mind. Bud has to get used to who Herman is, what he is like, and why.