As a non-muslim or a Muslim what ever you are, since I have been hearing a claim I ask this question. How many people do you think wrote the Qur'an and what's your reasoning or evidence behind it? How have you established it with what kind of scholarship?
Thanks.
If you want to look at it purely from scholarship view, without considering beliefs, It is hard to prove with absolute certainty how many authors wrote it.
According to historical narratives, and assuming that history is accurate, some people had memorized different Surrahs or Parts of the Qur'an, and had written them down, and kept it.
There are scholars that say, the reason that they had written them, was not that, they were planning to compile them into one Book. But they had written them, to assist them to remember for themselves.
How accurately it was written, we cannot be sure, as seal of Muhammad was not on them for authentication.
Once Muhammad passed away, it is said, that Umar and a group of other Muslims, collected the Surrahs from different people and compiled them. There, they ended of having 14 different versions of the Quran, with some differences.
We don't know for sure how different they were.
Umar ordered to keep one, and burn the other 13. We don't know how different the other 13 were.
Now, depends on what you mean by Author.
Based on beliefs, only Muhammad had said the verses, and thus He would be the one Author.
Is it possible that, some of the verses or Surrahs were added by others? It is hard to know with absolute certainty.