The Conversion Episode

On Shavuot, a Jewish holiday celebrating the people of Israel receiving the Torah from God at Mt. Sinai, we the read the Book of Ruth, the story of a Moabite woman, Ruth, who marries an Israelite man and, when he dies, remains loyal to her mother-in-law, Naomi, and returns with her to Judea. So, why do we read this story on Shavuot? It may have something to do with Ruth the Moabite being considered (however erroneously) the first ever convert to Judaism.