Why do Max and Liesel become friends?

I think that Max and Liesel are kindred spirits. They are both in a similar situation. Both have left their respective families and have been adopted by the Hubermans. Unfortunately Max must hide in their basement cellar. Although Liesel is nervous meeting Max at first, they quickly become good friends. They share nightmares as their first discussion together. Max has left his family and Liesel has lost her brother. Sharing their misfortunes the two become connected through sharing their souls and the printed word. Liesel teaches Max that he can express his scrappy personality through words and Max teaches Liesel never to give up. Both these traits prove essential themes in the story.