Koran: Rules for Wife Beating
If you need the Koran to tell you something as obvious as "beating your wife is immoral" — then you wouldn’t actually ever come to think that "beating your wife is immoral," because the Koran never says that.
But the Koran does mention beating one's wife ... so what does it say about the matter?
I’ve listed a verse from the Koran with 3 different translations and provided a link to the USC-MSA Compendium of Muslim Texts:
YUSUFALI: Men are the protectors and maintainers of women, because Allah has given the one more (strength) than the other, and because they support them from their means. Therefore the righteous women are devoutly obedient, and guard in (the husband's) absence what Allah would have them guard. As to those women on whose part ye fear disloyalty and ill-conduct, admonish them (first), (Next), refuse to share their beds, (And last) beat them (lightly); but if they return to obedience, seek not against them Means (of annoyance): For Allah is Most High, great (above you all).
PICKTHAL: Men are in charge of women, because Allah hath made the one of them to excel the other, and because they spend of their property (for the support of women). So good women are the obedient, guarding in secret that which Allah hath guarded. As for those from whom ye fear rebellion, admonish them and banish them to beds apart, and scourge them. Then if they obey you, seek not a way against them. Lo! Allah is ever High, Exalted, Great.
SHAKIR: Men are the maintainers of women because Allah has made some of them to excel others and because they spend out of their property; the good women are therefore obedient, guarding the unseen as Allah has guarded; and (as to) those on whose part you fear desertion, admonish them, and leave them alone in the sleeping-places and beat them; then if they obey you, do not seek a way against them; surely Allah is High, Great.
I would list this as another answer to the question: Why does it matter what other people believe?
So, why does it matter what people believe? Well, for one, if you believe that beating your wife is specifically allowed by the creator of the universe, that might shape your views on the matter, and in a negative way (to put it mildly).
Wife beating is just one entry on a long list of moral reasons to oppose religion in general, and Islam in particular.
When I read books relating to theism and atheism, I generally try to read argumentative books (from all kinds of perspectives). I do not read these books to try to motivate myself further into believing that religion is harmful, I have enough reasons already to believe so (See my essay: Why engage in religious debates). That being said, to have a great first-hand view of some of the consequences of this theistic kind of thinking, I recommend reading Ayaan Hirsi Ali's book, Infidel:
The book tells the true story of Ayaan Hirsi Ali's amazing life experiences. One of her primary concerns is the plight of women in Islam, and what she is trying to bring to light many unsavory aspects of Islam that cause real harm.