How do personal symbols of characters in the book help show characterization?

Sure, Max's accordion represents the kindness of Hans and the good cheer he brings.

Mein Kampf is a strong symbol of conformity to Nazi ideology.Reading it is kind of like reading the Bible today in a bus or train; people think you are committed to the ideas. Showing you are reading it provides a good cover for people who loath it. Hans gives it to Max to avoid suspicion. Max also paints the pages white and writes the The Standover Man and The Word Shaker on them. THe irony is priceless.