Other areas of interest have been the letters of the New Testament, especially the Letter of James, and the culture of the Graeco-Roman world as relates to such matters as: religion, spirituality, cultic associations, ethnic sub-groups and their ancient organization, professional societies and the general conditions of the societies in the Near East during the time of Second Temple Judaism, the time of Jesus and the formation of the Bible as we know it.
Published in 2006, Kloppenborg's book, The Tenants in the Vineyard: Ideology, Economics, and Agrarian Conflict in Jewish Palestine, titled after the "tenants in the vineyard" parable attributed to Jesus by the New Testament, provides an analysis for the critical reader of the Bible of this very difficult parable.
Kloppenborg also includes a second volume documenting historical papyrus dealing with ancient viticulture and agrarian conflict.
Their work also seeks to "document the major turning points in the history of Q research, with particular attention to the problem of establishing a critical text of Q" (xix).
Putting aside "a purely hypothetical Aramaic source" of Matthew and Luke, which would mean that "Q would never be more than a hypothesis," Robinson claims, in the introduction, that such approaches have been "completely replaced by objective criteria, based on empirical observation of Matthean and Lukan redactional traits" (xix).
The volume also contains a discussion of divergences from the Lukan sequence (lxxxix), text-critical notes (xc-cvi), and end-pages (cvii).