Danny's future has been laid out since birth: he will inherit his father's position as Rabbi and will have an arranged marriage. The problem is that Danny is a genius with a love for psychology. He does not want to take his father's place, but his father never speaks to him about anything but the Torah, so he doesn't know how to tell him.
The book is a wonderful picture of what Jewish life was like in America following the Holocaust, as well as a great depiction of a friendship (it follows the boys from childhood through their college graduation). You don't have to be Jewish or know that much about Judaism to understand and enjoy the book--virtually everything is explained. It really is just a great story.