From a Christian perspective, then, Old Testament theology is a truncated exercise, but a defensible one. In contrast, New Testament theology seems not only a truncated exercise, but also an indefensible one. It deconstructs. One of the New Testament’s own convictions is that the Old Testament is part of the Scriptures (indeed, is the Scriptures), give or take some questions about its boundaries, and that the Old Testament provides the theological framework within which Jesus needs to be understood. The New Testament is then a series of Christian and ecclesial footnotes to the Old Testament, and one cannot produce a theology out of footnotes.
There may be a hint of bias in Old Testament scholar John Goldinagay's words, but the man has a point. Nevertheless, there are four books in the New Testament that stand as a stumbling block. The irony is that they are probably the four books most overlooked when it comes to developing what might be considered a "New Testament theology". They are of course Matthew, Mark, Luke, and John. Footnotes they are not.
That being said, the Gospels might arguably feel more at home in the OT rather than the NT. What do you reckon? Would that transform our reading of the Bible, perhaps helping to bridge the gap between the testaments? Do pipe up, so I can call the people of NIV before it's too late!