This little book (Experiencing the Trinity) is by Joe Thorn, an American Baptist author new to me. It is made up of 50 short pieces on Father, Son and Holy Spirit, written out of the background of a struggle with some sort of depression. He says he wrote it for himself. I think that is a good way to write some books. It works here. The book is deceptively slight but would repay careful perusal, especially for someone is just heading out of a rough patch. More here. (A book with the same title came out some years ago. Do not confuse the two.)
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.