No modern biographer would ignore all of Jesus' early life, as Mark does, or skip over his formative experiences as a young adult, as all Gospels but Luke do (Luke 2:41-52). Nor would a modern biographer of John Fitzgerald Kennedy, for example, spend half of his account on just the last week of his subject's life, even if the person died tragically. And most modern historical works at least attempt to present themselves as reasonably objective.
But the authors of the four Gospels broke all these rules, especially the last. They were not disinterested observers of Jesus and his movement. No author who launches his work with the phrase "The beginning of the gospel about Jesus Christ, the Son of God" is pretending to write as a neutral reporter.
If the Gospels are not like modern works of history, neither are they like folklore. The time gap between the death of Jesus and the writing of the Jesus traditions (between 30 and 60 years) is too short to consider the Gospels as mere legends or folklore, which always have long gestation periods.
If they are neither modern biographies nor legends, what type of history do these Gospels contain? What do they reveal about Jesus? I believe upon close reading that three of the Gospels (Matthew, Mark, and John) are ancient biographies, and one (Luke) presents itself as an ancient history.
The Gospels were not written to give a chronology of Jesus' ministry as much as to reveal who he was. Even markers that seem to be precise were only devices to move the narrative along. Mark, for example, frequently uses the term immediately in transitions, but he usually only means "after that."
The authors did not have access to the extensive sources available today; besides, they were more ...