How do I pray? How do I study the Bible? How do I worship? How do I serve? How do I become a good steward? These are the questions every Christian should be asking. The answers are what every Christian needs to know. In Five Things Every Christian Needs to Grow, acclaimed theologian Dr. R.C. Sproul guides his readers through the basic training of Christianity and reveals the five most vital fundamentals of the Christian faith: Prayer, Worship, Service, Study, and Stewardship.
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.