The Banner of Truth Trust have just launched their first 10 books in e-format (kindle and epub). A nice option is that you can buy the book and the e-publication at a set price. Nothing being given away here but it's good progress ( I notice that here you can get the Thomas Case volume for 77p here or for 1.95 here so be careful). See 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.