Why Does The Torah Begin with Bereishit?

The Torah begins with Bereshit- Genesis, the story of creation. The question is, why? The Torah is not a history book it is the divine coding of creation and should have begun with the first Mitzvah in the Torah- the sanctification of the moon or time. The first Rashi (Rabbi Shlomi Yitzchaki- 12th Century France) gives us an insight into which many spiritual masters expanded upon.