I'm gonna nitpick here. Muhammed didn't "write" the Koran because he was illiterate and the Koran was not put to paper until at least a century after his death. The official story is that Muhammed recited verses that were "revealed" to him, but the evidence suggests that he made it up as he went along.
If you can stomach it, I stronly recommend that you acquaint yourself with Islamic scripture. It is the ugliest body of literature in the history of humankind (on a par with Mein Kampf IMO) and we will not defeat our enemies until we fully understand their motives, their goals and the depth of depravity that they regard as proper behaviour.