Often times the bible is just not the way we would write it. It would seem more logical that Adam and Eve were not to eat of the tree of the knowledge of evil. The tree gave them the knowledge of both good and evil, which they did not have until they ate from the forbidden fruit. This is not really all that hard to understand, until they experienced disobedience to God they never knew that there was good and evil. The word "good" just meant functional, they did not know anything about the reality of functional and nonfunctional...they were just innocent people that were living a life that had all their needs met and they knew God, since they had no knowledge of anything beyond that they therefore had no understanding that there was anything else. Like a baby in the womb of it's mother, it does not know good or evil, it just knows that it is alive.