why is the novel a tragedy

Fahrenheit 451 is a tragedy in that the main character goes from a happily married man who loves his job, to a man who leaves everything in search of purpose and value. I've never considered this aspect a tragedy........... I actually have always seen it as a coming of age.

Montag shouldn't have enjoyed book burning, and I thought it was fantastic when he began to see the value of the things being destroyed all around him. His world is filled with oppression, society is censored, and no one seeks the unknown. Seeing the final atomic destruction of the city he has lived in is indeed a tragedy. But in answer to your last question; the ray of hope comes from the books and information these men who've gone underground have stored in their minds. The past will live on through them, enabling them to eventually bring back society the way it was meant to be.