One of the classic works on Biblical Theology is a book entitled Biblical Theology by Geerhardus Vos. He defined biblical theology as follows:
"Biblical Theology is that branch of Exegetical Theology which deals with the process of the self revelation of God deposited in the Bible" (p. 13)
He then notes four main features of God's self-revelation in Scripture:
1. The historic progressiveness of the revelation-process. Revelation does not stand alone, but is inseperably attached to God's redemptive actions.
2. The actual embodiment of revelation in history. Revelation is incarnate in history, not merely incidental to it.
3. The organic nature of the historic process observable in revalation. Revelation and redemption move forward progressively not in a uniform sense, but often in bursts.
4. The fourth aspect of revelation determinative of the study of Biblical Theology consists in its practical adaptability. God's self-revelation is not exclusively or primarily for our intellectual advancement, but for the living out of God's purposes in the world.
Although originally written in 1948, Vos's work remains a must-read for those interested in biblical theology.