So a guy walks into a cabin and meets a black woman, a Jewish guy and an Asian spirit-being. Turns out they're the Trinity. It's not the beginning of a joke; it's the premise of a privately published Christian novel, THE SHACK, that's become a surprise best seller. The guy, Mack, is returning to the shack where his youngest daughter was murdered three years earlier. God, or Papa, as she is known in the book, has invited Mack over to talk love, pain and more love. (The Jew is Jesus, and the Asian is the Holy Spirit.) The story becomes a standard guy-meets-God melodrama, heavy on the heartstrings and full of torrid and often turgid dialogue. The unorthodoxy of the representation of the Triune deity (Ellen DeGeneres also imagined the Almighty as a black woman in a routine) has delighted some Christians and upset others. William P. Young, the 53-year-old father of six who wrote the book in 2005 as a way of explaining his faith to his kids, takes some swipes at the church and turns the weep meter to 11. Largely on word of mouth, the novel has been a New York Times trade-paperback best seller for five weeks. There's talk, natch, of a movie. Does this mean Oprah finally gets to play God?