[T]he theology to be introduced here is evangelical theology. The qualifying attribute “evangelical” recalls both the New Testament and at the same time the Reformation of the sixteenth century. Therefore, it may be taken as a dual affirmation: the theology to be considered here is the one which, nourished by the hidden sources of the documents of Israel’s history, first achieved unambiguous expression in the writings of the New Testament evangelists, apostles, and prophets; it is also, moreover, the theology newly discovered and accepted by the Reformation of the sixteenth century. The expression “evangelical,” however, cannot and should not be intended and understood in a confessional, that is, in a denominational and exclusive, sense. This is forbidden first of all by the elementary fact that “evangelical” refers primarily and decisively to the Bible, which is in some way respected by all confessions. Not all so-called “Protestant” theology is evangelical theology; moreover, there is also evangelical theology in the Roman Catholic and Eastern orthodox worlds, as well as in many later variations, including deteriorations, of the Reformation departure. What the word “evangelical” will objectively designate is that theology which treats of the God of the Gospel. “Evangelical” signifies the “catholic,” ecumenical (not to say “conciliar”) continuity and unity of this theology. Such theology intends to apprehend, to understand, and to speak of the God of the Gospel, in the midst of the variety of other theologies and (without any value-judgment being implied) in distinction from them. This is the God who reveals himself in the Gospel, who himself speaks to men and acts among and upon them. Wherever he becomes the object of human science, both its source and its norm, there is evangelical theology.Karl Barth, Evangelical Theology: An Introduction (trans. Grover Foley; Great Britain: Collins, 1963), 11-12.
Anything that makes us ponder the meaning of "evangelical" in "evangelical theology" is worth reading!
Also in the introduction (p. 9) Barth says "But many things can be meant by the word 'God'." This reminded me of NT Wright and his book NTPG who is consistent, albeit eccentric, in his use of "god" in the lower case on the grounds that the word does not have any meaning until you define it. I'm assuming that the goal of COQG (Christians Origins and the Question of God) is take readers from "god" to "God revealed in Jesus Christ".