In order to accept the Quran, or any religious text, as the direct word of God, you would have to accept it as a fact. in order for something to be a fact it has to be proven or able to be verified. Therefore, it is subjective. Some may consider it the word of God and others may not.
The Quran, as well as the Bible, the Torah, and other holy documents proclaiming to be the word of God were all written by people. It might be a fact that God emanates through the human mind and indirectly influences the thoughts of these controversial and historical writings. Undoubtedly the Quran contains words of wisdom and bits of truth, like the others. But no holy book could be the "direct" word of God for that would be absolute and permanent in a changing and temporal world.