So many people misunderstand the Two Trees in the Genesis account that I thought I would give it some mythological reworking, Lord of the Rings style, to illustrate the nature of the Tree of Knowledge of Good and Evil more clearly for people who know movies well, but bibles not so much.
For the fruit of the first tree, the Tree of Knowledge of Good and Evil, is not the key to all knowledge. It is only the key to knowing good and evil. And when you consider that prior to this Adam and Eve only knew good, well, there is only one half of the equation that they lack.
Mythologically this fruit functions much the same as the Ring of Sauron in the Lord of the Rings. It is the embodiment of self centred will. A tempation that is best left alone, as did the true companions of the ring bearer.