He will be the next Spiderman so I thought I should take a look at his past.
Do you give second chances? Haven't you ever said "he/she cheated on me and doesn't deserve a second chance!"? I bet you have (but hope you didn't have to). This movie is about the matter of whether there are some actions that deprive you of the right to a second chance or not.
Jack Burridge (Andrew Garfield) did something really bad (euphemism, for sure) and was given a second chance in life. He used it in a very good way. He tried to be a better person than the average one because he believed that he owed that to society. Guilt can be a very useful feeling for others but it can be unbarable for the person in which it exists. The movie succeeds in showing how difficult it is for Jack to adjust to a life he has no experience of (he was in prison for many years) and to carry the fear of his identity being exposed (only the person who is responsible for him knows his past).
We see what he did as a child and how he came to do it. It's one of these cases where it's easy to (kind of) understand why he did that terrible thing but it's also easy to understand why people hated him even after all these years.
Personally, I couln't help but root for him. I really wanted him to be happy with the girl he liked and to lead a happy life in general. But that was because the movie let me watch him. I could see his eyes, guess his thoughts, feel what he felt. For the viewers, he is not just a guy who did something horrible to a person we either knew or at least lived close to.
I don't know how I'd react if I learned that a person I work and hang out with was a murderer. I would probably push him/her away as fast as I could. But this film told me that there are choices. You can let your hatred and fear guide you and you can see the person who is standing in front of you right now. You can think about what this person is and not what it was. You don't have to forgive. You can just evaluate and appreciate. You can also remember that nasty actions are what they are whether they're towards an inoccent or a criminal.
Garfield is just spectacular as a young man who tries to start a new, happy life but does not fully understand how to communicate with others and is constantly burdened by the knowledge of what he's done as well as his hiding it.