The latest edition of the Evangelical Library organ In Writing is now out. it goes free to all Library members. The main item is Ian Hamilton's piece on Old Princeton from last June. See here for the Library website .
Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culture here. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.