Pip grows up in the country being brought up "by hand" by his shrewish older sister & her gentle husband. Joe, Pip's brother-in-law, is actually Pip's greatest childhood friend. Joe is a simple & ignorant blacksmith, but his kindness & care for others makes you realize how wise he actually is. Joe & Pip simply live for the day that Pip will be apprenticed to Joe & then "what larks!" they will have together. But a series of events that seem to be unrelated conspire to make Pip wish to be more than he ever thought he could be, & to then give him the means to that end.
Great Expectations is about the foolishness of youth & about growing up & leaving behind those that we love. It's about the abandoning of the people that made you good in favor of those that you think will make you great. And it's about the journey back home after being led far afield.
It's also a book about judgement. I can't tell you how many times I've labeled people in my mind based on some small aspect of their character that I think I've had some sort of special insight into. It's all rubbish. The label always comes from within the labeler-- you see something of yourself you'd rather not like to admit to in someone else. There are several quotes from this book that I like, but by far my favorite is one where Pip refers to his great friend Herbert:
We owed so much to Herbert's ever cheerful industry and readiness, that I often wondered how I had conceived that old idea of his inaptitude, until I was one day enlightened by the reflection, that perhaps the inaptitude had never been in him at all, but had been in me.
Thanks Mr. Dickens.