A few things need to be clarified.
It is not known that Mohamed was illiterate. He was the top man who worked for a wealthy merchant and made many long trips to into Arabia and Syria with valuable cargo, made deals and returned with traded goods. It is likely that someone in his position and influence and who had family members who were leaders of his city, that he was able to in fact read and write. Sure the Koran and Hadith alludes that he was illiterate but it also says that "Adam was formed from a clot of congealed blood" too, so I think it is fair to say that we can take the Koran with a grain of salt.
The Koran if not written at least in part by Mohamed was at least written UNDER HIS SUPERVISION so it is neither here nor there who actually wrote it. When Mohamed died (as a result from the poisoning of his food by his captive Jewish sex slave three years earlier) he left nothing but a pile of papers that had to be collected by his followers and put into some order. There was no end of story or accomplishment in the Koran. There was no original Koran. It just ended when Mohamed ended.
Many of the verses were found and burnt by Muslims because they did not fit into Mohamed's line of thinking as he progressed. An example of this would be the Satanic Verses where Mohamed proclaimed for a time that Allah existed with his daughters godesses; from Alah's relationship with the Sun godess. These verses were systematically searched for found an most of them destroyed. Another, according to Mohammed's wife, Aysha, with whom he resided at this death, was kept under their bed at the time of Mohammed's death, but was eaten by a domestic animal. References: Musnad Ahmad bin Hanbal. vol. 6. page 269;
Mohammed's child bride, Aysha, said this after he died:
"The verse of the stoning and of suckling an adult ten times were revealed, and they were (written) on a paper and kept under my bed. When the messenger of Allah expired and we were preoccupied with his death, a goat entered and ate away the paper."
In 1972 in the Great Mosque of Yemen was found and ancient bag of decaying Korans (the earliest found). They differ from the Koran as it reads today in quite a few places proving that the Koran is not the "sacred copy of the version kept in a tablet in heaven."
THE ASTUTE BLOGGERS: THE SANA QURANS: PROOF THE KORAN IS A POORLY WRITTEN, TERRIBLY EDITED AND TOTALLY MISINFORMED BOOK, AND NOT THE REVELATION OF A PROPHET... The devastating truth is that a large number of ancient Quranic manuscripts, dating from first century of Hijra were discovered in the Great Mosque of Sana’a (Yemen), which significantly differs from the present standard one. Carbon dating system confirmed that these Qurans are not forged one by religious rivalries. Moreover, these Qurans were discovered by Muslims, not infidels.
This is, probably, the most embarrassing event to Muslims in the 1,400-year history of Islam.
... Until now, only three ancient copies of the Quran are found. The one preserved in the British Library in London, dates from the late seventh century and was thought to be the oldest one. But the Sana’a manuscripts are even older. Moreover, these manuscripts are written in a script that originates from the Hijaz—the region of Arabia where prophet Muhammad lived, which makes them not only the oldest to have survived, but one of the earliest authentic copies of the Quran ever.
... As if it is not enough, many manuscripts showed the sign of palimpsests, i.e., versions very clearly written over even earlier washed off versions. The underwriting of palimpsest is, of course, often difficult to read visually, but modern tools, such as ultraviolet photography, can highlight them. It suggests that the Sana’a manuscripts are not only variants to the present version of the Quran, but the Sana’a manuscripts themselves were variants of earlier version, re-written on the same paper. It means, Allah’s claim that original text is preserved in heaven on golden tablets (Q 56: 77–78; 85:21–22), which none can touch except angels is also a fairy-tale.
Furthermore are the 35,000 microfilms have showed up.
Asia Times Online :: Middle East News, Iraq, Iran current affairs
Before the Yemeni authorities shut the door to Western scholars, two German academics, Gerhard R Puin and H C Graf von Bothmer, made 35,000 microfilm copies, which remain at the University of the Saarland. Many scholars believe that the German archive, which includes photocopies of manuscripts as old as 700 AD, will provide more evidence of variation in the Koran.
Given the abundant evidence I think it is only fair to say that it appears that Mohamed may have simply been a man with the personality of a Charles Manson who made up stories using bits and pieces form Zoroastrian, Jewish and Christian sources that he had picked up in his travels. His first wife had family members who were of a Christians sect and it is written than Mohamed used to meet with a certain hermit "monk" during his trips as a merchant into Syria. (That was before he started raiding and looting merchant camel trains) Allah was known as a name by some pagan Arabs for their Moon god. We have ancient Arab archaeological finds that confirm this. The Moon is a symbol all over Arab countries dating back to Pagan times and has been adopted by Islam. I think it is therefore a just a matter of closing the case.