Atheists often try to discredit faith and belittle the believers by calling the bible a work of fiction. They're wrong, of course. Fiction implies writers who know they're writing something false or inaccurate. In the bible, we see just the opposite. These are writers fully aware they're writing something fantastic, but also fully convinced their story is both true and accurate.
It's not just the writers either. If you look at the process and the people involved in compiling the New Testament, you'll see they too were deeply concerned with making sure the finished work was as credible as possible. They discarded as much work as they included for that very reason. Some of the work they discarded still exists and you can compare it to the work that made it into the New Testament to see why they might have rejected it.
I can't make any claim about the credibility and reliability of the finished bible, because there are parts which seem exaggerated or inaccurate, but it's pretty clear that the people involved were trying to get it as right as they possibly could.
Calling the bible "fiction" attempts to dismiss it, only you can't dismiss it that easily. There were too many people involved, over too long a period of time to just dismiss it. We don't always know what the bible is or means, but, clearly there's a lot more going on here than just fiction.