In the same section of Waterstones where I saw the Jhumpa Lahiri short story collection I saw a copy of Herman Hesse's Siddhartha. I first became aware of this book many years ago reading James W Sire's very helpful book The Universe Next Door. He mentions it in his chapter on Basic Eastern Pantheistic Monism. The book is certainly a great advertisement for that way of thinking. It relates the story of the eponymous hero from his Brahmin youth, through his time as a samana and encountering the Buddha, through a sansara period of sex, riches and gambling then back into a more traditionally Hindu approach to life. It is very well written and so lures in the unsuspecting. It was written (in German) in the twenties but reached popular heights only by the sixties when the Beatles and others were looking east for inspiration. It is still worth a read - in order to understand eastern thought and read well written and simple prose.
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.