The Gospel of Mark is considered by many as the oldest gospel of the bible. It's the second of the four gospels and the second book of the new testament. It's also the shortest gospel with 16 chapters where the last 8 verses of chapter 16 are not recognized by some scholars. The Jehovah witness bible for example does not accept the last 8 verses of Mark as authentic.
Gospel style is unique in the sense that he projects Jesus as the great celebrity followed by the masses. He focus in the miracles and the multitudes following the master.