Jafar, it's true that the Qur'an uses fear and pleasure in its text. But in my experience, a lot of books do that, including the New Testament.
There is a component in the Qur'an that makes it psychologically effective. I think it maybe has to do with the emotion called "regret". Overall, the Qur'an is filled with plausible after-life scenarios that trigger this. Whoever wrote the Qur'an mastered this form of visualization of regret (i.e. "If only you only knew!" and "This world is temporary and you're going to regret investing in it."). It exceeds main exposition of describing hell. You actually feel as if you're in a courtroom of sorts since its judging your current actions in real time. Like I said, I'm speaking about this APART from making a value statement on the Qur'ans nature. Whether it is peace or violent is another discussion I think. I'm just probing its effectiveness.