As much as Shavuot commemorates the giving of the Torah, Simchat Torah is designated as the day we celebrate being given the ultimate gift. Shavuot is a recognition of the revelation at Mount Sinai. Judaism began with every Jew hearing Hashem speak. That was Shavuot.
Simchat Torah is our opportunity to rejoice and recognize how this book was the greatest gift given not only to the Jewish people but to all of mankind. The Torah would not allow man to sink to the level of the animal.
It was not enough that Avraham Avinu was charged with the task of teaching the world the idea of monotheism. The entire Jewish nation were meant to teach morality to a world that was interested in power seeking and self gratification.
We are expected to delve into the teachings of the Torah in greater depth each year. It is a good time to take upon ourselves to study the weekly Parsha with a new commentary so as to gain new insights and meaning to the greatest and holiest book ever written.