There is much ancient Jewish literature, oral and written, outside the canon which was very much a part of Jewish worship since the time of Moses and even Noah. It sheds light on parts of the canon which are very brief. That's why Prof Kugel spent a big part of his career on the Book of Jubilees.
As an aside, though Prof Kugel is an Othodox Jew, he and his books are held in high regard by many Christian authorities on the Bible.
Most Protestants take no account of Jewish writings after the time of Ezra. But unless they read the Apocrypha (which were included in the early editions of the KJB but omitted since about 1650) they have to depend on Josephus to, shall we say, set the stage for the coming of Jesus. How many know, for instance, the history of the Hasmonean dynasty which preceded the Herodians?