The Koran is the Bible of Islam. Revealed to the world by Muhammad approximately 1,400 years ago, it is regarded by Muslims, universally, as the word of God to Muhammad and from him to all Islam. No devout Muslim disputes this; in this respect, there is more agreement among Muslims about the divine origin of the Koran (seen as having been literally dictated to Muhammad by the mouth of Allah Himself) than there is about the origins of the Bible among Christians.
Even those of us forced to rely on translations of the Koran (considered interpretations of same because only the Arabic Koran is the literal Word of God) can see the literary value of this work. There is tremendous spiritual and psychological value in reading this book, as well, for Muslim and non-Muslim alike.
For me, the psychological value of this book comes in its emphasis on right and wrong belief and standing up for what you believe in, even if it costs you dearly in terms of human relationships. Certainly, no one has accused Muslims of being wishy-washy about their faith! In fact, the differences in the various branches of Islam come from the ways in which they practice their faith. A Sunni Muslim will differ from a Shi'ite or Twelver Muslim in the way in which they practice their faith, but they will not disagree about the divine origin of the Koran or the fact that there are correct and incorrect beliefs. I think that Catholics and Protestants can learn an important lesson from Muslims in this regard; we have become so concerned with whether or not the Bible is inspired or dictated directly from the mouth of the Lord, or whether certain beliefs are correct or incorrect, or whether certain actions or practices are moral or immoral, that we are no longer truly Christian or loving of one another.
The Koran basically mandates certain behavior from the rank-and-file believer. In this respect, Islam is less a religion than a way of life and pattern of behavior with Allah (God) at its very center. By way of contrast, Christians leave Christianity at the door of church on Sunday, still practicing that civil religion so popular during the 1950s and so offensive to those of us who take the Bible and Christ seriously. Muslims are expected to pray five times daily; Christians who pray once daily are seen as "out of the loop" and are thus discouraged from contacting God regularly unless it's to be polite during a worship service. Muslims fast at least one month a year; Christians generally ignore the need to undergo cycles of feasting and fasting, unless they belong to a denomination which takes Lent seriously. Muslims consider charitable donations a tax of sorts, due and payable once a year during the feast of Eid, one of the five pillars of the faith without which one is not a Muslim; Christians generally donate to charity with such highhandedness and snobbery that they might as well not donate one penny.
I would strongly recommend that people of all religious persuasions read the Koran, if only to learn more about what Islam really is all about.