In her autobiography Frances Ridley Havergal tells how as a very young girl she was struck by a hell fire sermon she heard that awoke her to her spiritual need. She says "No one ever knew it, but this sermon haunted me, and day and night it crossed me." It is that "No one ever knew it" that strikes me. It is an encouragement to every preacher who is faithful. Who knows what a sermon may do.
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.