A Textual Commentary on the NT
Those interested in text-critical questions about the Greek NT will find very helpful as a first resource to consult: A Textual Commentary on the Greek New Testament, Second Edition, Bruce M. Metzger (on behalf of and in cooperation with the Editorial Committee of the United Bible Societies’ Greek New Testament). Stuttgart: United Bible Societies, 1994.
NT scholars will know the work, but I mention it for the benefit of the many “lay/general” readers of this blog-site, as well as those who may be scholars in other fields, who are keen to know more about text-critical matters.
This work gives data and analysis on the places of textual variation noted in the United Bible Societies’ Greek New Testament, but these include pretty much all the really major ones. At each point the commentary lays out the evidence and then gives the rationale for the decision made by the committee that produced the UBS Greek New Testament as to which variant to prefer.
So, for example, to refer to a couple of points of textual variation mentioned in an earlier posting, the data on the “Pericope of the Adulteress” are discussed in pp. 187-89, and the thorny issue of the endings of Mark in pp. 102-7.