Why does Liesel steal books in The Book Thief?

In the beginning of the book Leisel and her mother have gone to the cemetery.  Liesal's mother had carried her brother's limp body there.  The grave diggers dig a burial site for her brother.   While there with her mother Liesel sees something.  She picks it up.  It is a book.  The title is "The Grave Digger's Handbook."

Liesal hangs onto the book.  Her mother sends her to live with a foster family in another town on Himmel Street.  Liesel rubs the book in her hands.  The book is all she has left to remind her of her brother. 

"***THE BOOKS MEANING***

1-The last time she saw her brother.

2-The last time she saw her mother.

Liesel is unable to read or write.  Yet, she wants to be able to read.  Hans Huberman her foster father begins to teach her how to read.  Books are in short supply so he teaches her to read the book she had stolen.  Liesel then steals books from book burnings by the Nazis and from the mayor's house.  Liesel has a thirst for knowledge and the books provide her with both knowledge and escape from the sadness of her mother's abandonment.