In The Book Thief, what does the act of book thievery teach Liesel about life and death, and how do these events reveal Liesel as a dynamic character?

The way it heads to Liesel's unlikely friendship with the wife of the Mayor, and how this friendship directs her to uncover the fierce sadness of desolation of the Mayor's wife's life and how she in a lot of ways is living like a dead person, although she's still alive, is one of interesting things about Liesel's book thievery.