There should be no fear, however, of allowing other ancient literature to inform our faith since some of that extrabiblical literature (the Apocrypha, Pseudepigrapha, and other early Christian literature) informed the faith of the earliest Christians and even later ones. And some of the noncanonical gospels may indeed contain a few authentic strands of the teachings and sayings of Jesus. [These are called agrapha.] If that is the case, why should Christians avoid listening to them, at least in a careful and critical manner? (428, cf. 8ff)As a matter of pastoral care, it is challenging to address Martin Luther's one-time opinions (later reversed) regarding James, Hebrews, Jude, and Revelation. It is unfortunate that the author only gives part of the Luther story (383).
The basics of criteria for inclusion are reinforced near the end of the text (405ff).