A little while aggo I came aross a book by a man called Tim Marshall called Prisoners of Geography. A very helpful book, it explained the geographical element in geo-politics - why China takes the atttiude to North Korea it does, some of the attitudes Russia shows over Ukraine, etc. It was very helpful and well written. I then noticed that he also has a book on flags - Worth dying for. I waited until the paperback came out and this again proved to be fascinating as it explained flag by flag the various flags of the nations and a few more too. Some of it read like a detective novel as he painstakingly traced the origins of some of these. I am not really a fan of politics but I like to keep up to some extent and I enjoy obscure knowlede and so this unusual little book was right up my street. (You may have noticed some lists about flags on this blog while I was readuing the volume).
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.