Ultimately there was very little new information in Mark that wasn't contained in more detail in Matthew. A few inconsistencies occurred, such as the colour of Jesus' robe when he was being mocked as the King of the Jews and a few other minor things, but these can be expected from a story that is coming from two different prospectives, a lot of the time from people who weren't there in person.
A couple of interesting points were reinforced during this book however, one being the concept of being "saved" (a very big thing in the American baptism brand of Christianity), being the only way to go to heaven (regardless of your actions), the other being the underlying hypocrisy of Christianity. I mean this not so much in the sense of within the bible or this specific book, but the human nature of it, extracting out parts that they wish to follow and include in their specific church's doctrine, and conveniently ignoring other pieces.
One example of this from both Matthew and Mark was the reference that to divorce your husband/wife then take another partner is a sin, and is considered adultery. Those familiar with English history will know that this is the very point that spawned the Chruch of England from Catholicism as Henry VIII wanted to divorce his wife and re-marry and the church at the time would not let him. To my knowledge most American churches currently allow divorce and to me this illustrates the human nature of religion, to make it convenient.
As I said Mark really threw up nothing new that wasn't contained previously, so I will not dwell on it.
Next up is Exodus, and back to the early days of the Earth where God was far more personally involved than my current experiences of Him in the new testament.