I. The Bible is unique
There is no comparison with any other works of mankind. No other books had anywhere near the number of contributors (39+), nor have any been written over such a long span of time (1,600 years). Yet it is profoundly cohesive in all of its contents.
Sort of, but not really.
No other books had anywhere near the number of contributors (39+)
There's plenty of works that have had large numbers of contributors. And if you allow collections of works, like the Bible is, then you should include things like the Encyclopdia Britannica, which according to wiki has over 4000 contributors.
nor have any been written over such a long span of time (1,600 years)
Have you heard of
Man'yōshū?
It a collection of Japanese poems and it goes back over 1,600 years.
So yeah, the Bible is neat and all, but its hardly as unique as you're trying to make it.