I was in the local library the other day and I saw a book I had never heard of by Leo Tolstoy. Being quite a short paperback, a novella, I thought I'd try it. Well, it's an amazing book! It is brilliantly written for starters. Then it deals with a vital subject that few books tackle - death. Finally, it actually deals to some extent with sin and salvation. I understand that it was the first book Tolstoy wrote after his "conversion". I hadn't realised that at all when I picked the book up so that has doubled the impact on me. It's great when something comes out of the blue like that. I also like it when someone like Tolstoy who is supposed to be brilliant turns out to be just that. Check it out. You can find it online here or buy it here.
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.