Now the question is, who wrote Quran or who was the author of Quran?
Hadith tells us that Muhammad was illiterate and was unable to read or write. So of course Muhammad did not write Quran. Muslims claim that Muhammad dictated the whole Quran to his followers and many of them memorized the Quranic verses word by word and later they wrote it down.
After the death of Muhammad there was a time when Uthman the third Caliph of Islam ordered to burn all the copies of Quran except one. It was believed that there were variations in text and recitation practice of Quran at that time and so Uthman took this step. According to Quran and Hadith, Muhammad was the last prophet of Islam. So Uthman was not a prophet and we do not know whether he kept the valid and original Quran or destroyed it? We also do not know how he determined which one was the correct version of Quran?
Muslims claim that Quran was directly given by Allah and Sheikh Ahmed Deedat the Muslim Scholar and other Muslims have claimed that Quran is the word of God because it was written in first person speech unlike Bible, where third person speech is used. But the very first chapter of Quran is written in the third person speech.
This is not the only one example but there are many Surahs which are written in third person speech. So if we take the word of Muslim Scholars, Quran is not the word of God.