In reply to ericinbristol:
This is quite useful :
http://www.amazon.co.uk/Why-I-Am-Not-Muslim/dp/1591020115
An anonymous or rather pseudonymous author, for obvious reasons.
For such inflamatory material, the writing is actually quite turgid and rather laboured - he clearly needed a good editor. But the basic points are sound, such as :
1) Mohamed, or someone very like him, almost certainly DID exist, i.e. we are talking about a real historical figure - a brutal, rapacious but very successful warlord in fact
2) Although quite clever and personally charming when he wanted to be, he was not in any normal sense an intellectual or scholar, probably illiterate, with very little in -depth understanding of any theology
3) Much of the Koran is highly derivative, i.e. it is pinched from a variety of sources, predominantly the Hebrew bible but also Babylonian creation stories, Zoroastrianism etc. But the borrowings frequently misunderstand or or are inaccurate versions of the originals
4) He was probably personally sincere in his view that he was receiving divine revelations, various diseases have been postulated as the cause of these delusions
5) Despite his general sincerity about his voices, he could also twist them to attack his personal enemies or for his own very material or rampant sexual desires
6) He had little understanding of ancient philosophical dilemmas, such as the clash between free will and fixed fate
The last is quite important, as it is the basis of everything being the will of Allah, including whether anyone accepts the "revelation" of Islamic truth or not. So "Allah" could reveal himself to everyone if he wanted, but chooses only to do so to his selected ones. Those who he does not do so, he tortures (described in very graphic, physical terms), in hell for eternity, though of course it is in no way their fault, since Allah choose not to reveal the truth to them. So the non-believing human beings are basically automata, being punished in vile ways, forever, for something that they had no agency about whatever, basically a whim of Allah.
If Mohamed had been more of a religious scholar, he would have been aware of the ancient philosophical problem of free will conflicting with divine intention and justice. But he wasn't, so his universe is a crude, mafia-boss style rule - do what I say, utterly uncritically, and you will get (very material and specific rewards in paradise, girls, wine, water, etc). Don't do what you are told and you will be tortured (again in a very specific physical form), forever. But actually you have no choice or agency in how you behave anyway.
In Bernard Shaw's play Major Barbara (a major in the Salvation Army), Barbara famously says :
"Let God's work be done for its own sake, I have got rid of the bribe of heaven".
There is no such concept in Islam, indeed, it is unthinkable in it.