Kids!

I think that Great Expectations is very similar to the book To Kill A Mockingbird.  One of the main similarities is both books are told in the same perspective.  In GE the story is told by Pip as he looks back at his adolescence.  He narrorates his life as he grows up and recalls his feelings and thoughts as he is reliving his expiriences.  In TKAM, Scout is also retelling her life when she is older by remembering her emotions.  A minor similarity is how both Scout and Pip's names are a kind of nickname they had acquired.

Both of these books have the similar theme of growing up.  They both show the main characters' transition from a child to a teenager.  Pip's story continues as the book takes place over many years but TKAM only shows a couple years of Scout's life.  A similar motif of consequence/penitance is shown in these books when Scout and Pip have to deal with their mistakes; Scout's with the children who tease her and Pip with the convict and his guilt. 

The two main children show the common human trait of wanting more then what they have.  Pip has a desire to become a gentleman and be a part of the rich society.  Scout wants everyone in her town to accept her family, especially her father,  but not everyone will like your opinion which is a lesson she needs to learn.