Amazing Spider-Man is effectively both a Deconstruction and Reconstruction of Spider-Man. The first part of the movie effectively tears apart the story of Spider-Man by subjecting it to reality. A heavier emphasis is placed on elements like Parker's feelings of parental abandonment over his parents' death. Uncle Ben is a simple, uneducated man instead of a fountain of instant wisdom, Parker is a loser who is so terrible at talking to the girl he likes that she has to ask him out, Flash Thompson is just a kid seeking the approval of his friends and lashing out at the world by picking on those weaker than him, etc.
Uncle Ben dies a pointless death that Parker fails to learn anything from, and Peter sets out on a reckless vendetta to hunt down a murderer that he probably won't ever find in a city of over a million people, becoming more of an angry thug than a superhero, while being hunted by police for being little more than an angry vigilante, a claim that rings very true in the film when it's put into words.
End result is: Spider-Man is a petty Jerkass who expects the world to revolve around him, can't control his powers, stole all his best technology, and uses superheroism as an excuse to lash out and hurt people to make himself feel better.
But about halfway through, something changes. Peter does something truly noble, learns to stop chasing petty vengeance and starts to actually learn the true meaning of responsibility in a way that echoes deeper than a few well-placed words and a guilty conscience. In taking responsibility for his mistakes, Parker learns to become the hero he was meant to be, and for the first time, actually becomes Spider-Man.
From there, we see his relationship with Gwen grow into something real, watch him make amends with his Aunt May, and finally get to hear the wisdom of a simple man in Ben's last message. The entire tone grows with him.
The first part of the film is all about reality tearing down the core elements of Spider-Man and telling a story of what would actually happen in the situation described in Spider-Manís origins. The second half is about taking those elements of reality and weaving them into the story to breathe new life into those core elements, resulting in a Spider-Man that is simultaneously more believable AND more true to the character than ever before.