The Bible's Purpose
Archimandrite Justin Popovich lays out the reasons for reading the Bible in "How to Read the Bible and Why":
All that is necessary for this world and the people in it--the Lord has stated in the Bible. In it He has given the answers to all questions. There is no question which can torment the human soul, and not find its answer, either directly or indirectly in the Bible.
In the Bible God make known:
what the world is; where came from; why it exists; what it is heading for; how it will end;
what man is; where he comes from; where he is going; what he is made of; what his purpose is; how he will end;
what animals and plants are; what their purpose is; what they are used for;
what good is; where it comes from; what it leads to; what its purpose is; how it is attained;
what evil is; where it comes from; how it came to exist; why it exists -how it will come to an end;
what the righteous are and what sinners are; how a sinner becomes righteous and how an arrogant righteous man becomes a sinner; how a man serves God and how he serves satan; the whole path from good to evil, from God to satan;
everything - from the beginning to the end; man is entire path from the body to God, from his conception in the womb to his resurrection from the dead;
what the history of the world is, the history of heaven and earth, the history of mankind; what their path, purpose, and end are.
Rev. Dr. Eugen J. Pentiuc expresses similar thoughts in "The Untamed Textbook and Its House-Trained Handouts":
Scripture is an open textbook, an endless reservoir of wisdom in the making. But above all, Scripture is a living and ever-refreshing means of communication with God, its primus auctor. ... Scripture is not, nor does it claim to be, a complete "recording" of God's mind. Rather, it is a means through which God re-creates us each time when we approach the Scripture, as he did on the sixth day when he breathed his breathing of life on the dust and the dust became a "living breath" of God (Gen 2:7). The Lord re-creates each reader of Scripture as a partner in dialogue with him, the source of life.
The Bible's Authority
In an episode of the Ancient Faith Today podcast called "The Eastern Orthodox Approach to the Bible," Presbytera Jeannie Constantinou says this about the nature of the Bible's authority:
First of all, the Church does not rely on the Bible for its doctrine. We don't rely on the Bible, because the Church came first. ... The Church knew what it believed about Christ before the books of the New Testament were written.
There is no question that the Bible is authority, so if I gave the impression that the Bible is not authority in the Church, that's certainly not true. It is authority, but it's not over the Church, it's not under the Church, it's part of the Church. It does stand as part of the Tradition, part of apostolic Tradition. It's just the written form of apostolic Tradition. To that extent, it's not exclusive authority.
For us we have this consistency through the centuries, because we read the early Church Fathers who comment on these, who use these verses, because we have them in our hymns and in our prayers, we understood what is meant by them, so they are less susceptible to being distorted by the individual opinions of people. We have a consensus of meaning within the Church, and we do not exceed that boundary. We don't substitute our own personal opinion.
The Bible and the "Word"
Constantinou elsewhere in the episode explains the relationship between Jesus, the Bible, and the term "Word of God":
The Bible is the Word of God because the message is from God, but the ultimate Word of God is Jesus Christ, because he is the ultimate revelation of God. As we said, human language has its limitations to describe or explain God, but Christ was unlimited. The apostles experienced God in the Person of Jesus. What they experienced went beyond human language.