the bible passes the test of historicity with flying colors. there is more manuscript evidence for the bible (especially the new testament documents) than any other book from the ancient world. the original texts from the new testament are dated within 20-60 years of the events described leaving no time for legendary development. there are enough ancient copies of the new testament (quoted in writings of the early church leaders) to feel confident that the text has not changed since it was written and the bible we have today is exactly as it was written. the discovery of the dead sea scrolls in the late 1940s confirmed the accuracy of certain old testament books as well.
an interesting side note is that all but one of the new testament authors was murdered for his faith and his refusal to recant what he had written and believed in. for me, that is one of the most compelling arguements in support of the historical accuracy of those documents. a lot of people will die for a lie (mohammed atta for example) but, i know of no one who would die for a lie knowing its a lie. those authors had first hand experience with Jesus and recorded certain events from their experience. they were, for the most part, poor uneducated fishermen who were put to death for their faith and refused to back down when given the opportunity. has a ring of authenticity to me.
if you cannot trust the bible as a reliable document, you cannot trust any book from the ancient world.
now, as far as why i believe the bible is the truth...well, that would take me hours and hours to type. i dont really mind doing it but, i feel that most people reading this thread would probably call me a moron, or a religious freak or some other endearing name. so, i dont think i'll take the time to do it in this forum.