The entire new testament is fan fiction. Iēsous of Nazareth didn't write any of it, the first assumed author never even met him.
The "biblical canon" of today seems to be more or less just whatever was later dictated when Christianity became the Roman Empire's state religion. Who knows how much other, potentially more accurate reports about Iēsous were lost during that dictatorship?
Now, I agree that Paradise Lost does not have any claim to veracity. I would just also say any claim the new testament has is null and void.