I like a good Christmas book and having spotted this reprint of J Jefferson Farjeon's Mystery in White last year and having bought it in a charity shop in the summer it was good to get it out recently and read it. This is not Agatha Christie but the plot is an intricate and more or less plausible one. It's great feature is lots of snow and references to Christmas which is what you want at this time of year. It originally appeared in 1937.
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.