As I understand it, it was normally adultRESSES who were stoned to death (and are, I believe, still stoned to death in some parts of the world today). That was because their societies were based on patrilineal descent. Men passed their 'property' on to their sons (i.e. male, genetic offspring) after death so they needed to ensure that any male heirs were descended from themselves and they didn't leave all of their worldly goods to some ' @#!*% ' resulting from the wife's indiscretion. So adultery was not originally a crime 'against God' but an economic one based on male dominance.
You haven't read the Bible then, because it is very clear on who is to be stoned, and it is certainly not just women. See Deuteronomy 22:22-24, which says: "If a man be found lying with a woman married to an husband, then they shall both of them die, both the man that lay with the woman, and the woman: so shalt thou put away evil from Israel. If a damsel that is a virgin be betrothed unto an husband, and a man find her in the city, and lie with her; Then ye shall bring them both out unto the gate of that city, and ye shall stone them with stones that they die; the damsel, because she cried not, being in the city; and the man, because he hath humbled his neighbor's wife: so thou shalt put away evil from among you."
Seems like God wasn't too worried about gender when he gave the death penalty for sins. And the fact that adultery is deserving of death shows that God thinks very highly of the marriage covenant. Marriage is the second most holy covenant ever, after God's covenant with a Christian. It's not broken lightly, and God will hold adulterers accountable for their actions (Matthew 5:28).
"Let God be true, and every man a liar!" (Romans 3:4)