It has taken a little longer than I had expected but I am hopeful that my book on What Jesus is doing now will be published by Evangelical Press next month. Available through the various channels I do hope it will be a help to many on what is sometimes a rather forgotten topic.
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.