What do you think of when you think of Andy Warhol? Campbell’s Soup? All-night parties? Pop-art album covers for the Rolling Stones? You might picture a slight, frail, near-albino artist in tortoise shell glasses, but you probably wouldn’t picture him in the back pew of a Catholic church, genuflecting devoutly. But that’s where he was, several times a week for his entire adult life, his devotion to Christ a quiet, even secret, affair. Few people knew that he was a regular at a New York City homeless shelter where he served meals and spoke tenderly with the visitors. Nor that he painted 60 pop-art versions of The Last Supper, an entire series of crosses, another one of Madonnas, a Colorform-esque painting of twelve eggs, symbolizing the disciples, and a Madison Avenue-style poster that proclaimed, “Heaven and Hell are just one breath away!” On his nightstand, where, if his public persona…