Before the destruction of the Temple in 70 AD, Aramaic-speaking Jews read and taught from the Hebrew Scriptures. Many books were considered religious in nature, but there was no precisely defined Jewish Canon of the Scriptures. The Jews of Samaria believed only the first five books of Scripture (Torah) were divinely inspired for they were the teachings given to Moses. However, the wider-held Pharisaic Tradition believed that the oral law, passed down from the time of Moses, including all the explanatory and supplementary writings deriving from it, were just as inspired and authoritative as the Torah.
The Greek-speaking Jews of Alexandria wanted the Septuagint to include translations not only from the written Torah but also from the books derived from the oral law (those of the Pharisaic Tradition). There is no question that the quality and style of the translations in the Septuagint vary considerably from book to book. After all they were translated by many different hands over more than two centuries.
When the translations began in 280 BC with the Torah (Pentateuch in Greek), few objections were voiced by Jewish authorities overseeing the project. The Septuagint was so highly regarded at the time of Jesus Christ, that the evangelists used it as their source document in writing the Gospels.
When Jewish scholars met at Jamnia in the last decade of the first century, the number of Hellenistic Jews in the Diaspora using the Septuagint significantly exceeded the number of Jews using the Hebrew Scriptures. The growth of Jewish conversions to Christianity owed a great debt to the reading and preaching from the Septuagint. Read more from Rock of the Apostles: A Brief History of Catholic Tradition (goo.gl/MPqLV6).