This is just to alert you to the June Banner of truth mag which includes an article by yours truly - God's sheep, as safe as safe can be. Do check it out. The boy on the cover is J C Ryle.
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.