As an adherent of a world religion (christianity) this is an important question. Is the bible true? Is it true that Jesus rose from the dead? What does Jesus mean when he says he is "The way, the truth and the life"?
The latter questions seem to hinge on how you answer the first; if the collection of words we call the bible is only a man made set of myths with no connection to any historical reality then the answers to the second two questions might be different. So if we say the bible is true, how is it true? Is it true like the news is true? Which news do you mean? The BBC or Fox, or the newsletter I got from a political party in May? And which bits of the bible are we wanting to call true? the historical narratives might be true, but what truth is there in a song of worship such as a Psalm?
If we want the historical narratives of Jesus' life to be true how are they true? Are they unbiased reports from dispassionate observers with perfect recall and photographic memories? or are they something else in which fact and interpretation are so closely intertwined you can't separate them.
I'm reading "New Testament Interpretation" by Ian Boxall, and "Christ Plays in Ten Thousand Places" by Eugene Peterson. Boxall points out that even the people who first observed the man Jesus and made a memory of what they had seen were already interpreting it and seeing it differently from others who had seen the same thing. I was at a meeting a couple of evenings ago; someone said something about a situation and I heard her concern and irritation with that situation in what she said and the way she said it. The following morning, someone else who had been at the meeting commented in a way that suggested she'd heard something quite different. I'm fascinated by that because everyone is telling the truth, as they see it, but we've already got three versions, and probably another one each for all the other people at the meeting. Imagine how many versions there must have been of the feeding of the five thousand!
Then we take our experience and we use words to communicate it but the words we use are inadequate to describe everything that went on, they only stand for the reality of what they describe, they aren't the reality of it. Peterson discusses the doctrine of the Trinity, describing it as a map of the country of God, but not God himself. It's related to the country and enables us to explore it, but it isn't the thing itself.
Sometimes the words we use are blatantly lies. Jesus did this a lot, except we call them parables. There was no specific rich man who sold everything he had to buy the pearl of great price, so this isn't a true story. But there is so much truth in it because it cuts to the heart of what Jesus was teaching about the Kingdom of God. There is truth at the core of the Harry Potter universe: the truth that a life laid down willingly because of love can have the power to conquer even death, yet Harry Potter is "only" fiction.
So what is the truth? My answer is that I don't know which bits of the bible are true in a factual sense but there is great truth in there mainly because it points me to the one who called himself the Truth. So my answer to the question is to say it’s the wrong question; the right question is Who is the truth? But these are just my words....