At the moment in Harry Potter and the Deathly Hallows Harry is looking at Snape's memories about his mother and his dealings with Dumbledore in the Pensieve. I find it intriguing how Snape loved Lily to the point where he would do everything he could to keep her son safe from Voldemort whenever he returned. Snape regularly put his life at risk by being Dumbledore's man on the inside of Voldemort's regime. He even took Dumbledore's life and gave his own to keep Harry safe. He also dealt with Harry being extraordinarily mad at him for all the things he had done which ultimately kept Harry safe.
I still do not understand why Lily married James. Whenever we hear her speak about him, it was not positive. I would like to know what happened to change their relationship. It might have something to do with the fact that they both were going to fighting Voldemort. This situation is confusing to me.