I was in a charity shop today when I saw this going for £5. It is a 1953 encyclopaedia edited by Gordon Stowell. A 1072 page comprehensive volume of facts with illustrations and maps it is the encyclopaedia we had at home when I was a boy and it brought back happy memories to see it again. I didn't buy it.
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.