Mark Twain or Samuel Langhorne Clemens (1835 – 1910) to use his real name (Mark Twain is a clever reference to soundings taken on the Mississippi River) has been a favourite of mine since childhood, even after discovering that he denied many of the things I hold dear. I've still only read Huck Finn and Tom Sawyer and a few shorter pieces but cherish the idea of getting on to The Prince and the Pauper (1881) A Connecticut Yankee in King Arthur's Court (1889) Pudd'nhead Wilson (1894) and some of the short stories.
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.